Tools

The TOOLS: section defines the external capabilities available to an agent. Each tool declares a typed signature (parameters and return type), an optional execution binding (HTTP, MCP, sandbox, or lambda), and metadata that guides the LLM’s tool selection.

Tool declaration syntax

A tool is declared with a function-style signature followed by indented properties:

TOOLS:
  tool_name(param1: type1, param2: type2 = default) -> ReturnType
    description: "What this tool does"
    type: http
    endpoint: "/api/path"
    method: POST

Signature format

name(parameters) -> return_type

name — a lowercase identifier using snake_case
parameters — comma-separated list of typed parameters
return_type — the type of data the tool returns

Parameter syntax

Each parameter follows the format name: type with an optional default value:

param_name: type
param_name: type = default_value

Component	Description	Examples
`name`	Parameter identifier (snake_case)	`account_id`, `query`, `limit`
`type`	Data type	`string`, `number`, `boolean`, `date`
`= default`	Default value (makes parameter optional)	`= 10`, `= "USD"`, `= true`

Parameters without a default value are required. Parameters with a default value are optional.

Parameter types

Type	Description	Examples
`string`	Text value	`"hello"`
`number`	Numeric value (integer or float)	`42`, `3.14`
`boolean`	True or false	`true`, `false`
`date`	Date value	`"2026-03-01"`
`object`	Nested object (specify fields with nested `parameters:`)	—
`type[]`	Array of the given type	`string[]`, `number[]`

Object parameters

When a parameter has type object, you can define nested fields using a parameters: block under the tool:

TOOLS:
  create_order(customer: object, items: object[]) -> {order_id: string}
    description: "Create a new order"
    parameters:
      customer:
        name: string
        email: string
      items:
        product_id: string
        quantity: number

Array parameters

Array types use the [] suffix:

TOOLS:
  bulk_lookup(ids: string[]) -> {results: object[]}
    description: "Look up multiple records by ID"

Return type

The return type appears after the -> arrow. It can be:

Form	Syntax	Example
Simple type	`-> type`	`-> string`
Object type	`-> {field: type, ...}`	`-> {id: string, name: string}`
Array type	`-> type[]`	`-> Hotel[]`
Nested object	`-> {field: {nested: type}}`	`-> {user: {name: string, age: number}}`
Optional fields	`-> {field?: type}`	`-> {error?: string}`
Array of objects	`-> {field: type}[]`	`-> {id: string, title: string}[]`

TOOLS:
  search_hotels(destination: string, checkin: date, checkout: date) -> {hotels: {id: string, name: string, price: number, rating: number}[], total: number}
    description: "Search available hotels"

Description

The description: property provides a natural-language explanation of what the tool does. The LLM uses this description to decide when and how to call the tool.

TOOLS:
  verify_account(account_id: string) -> {name: string, status: string}
    description: "Retrieve account details and verify the account is active"

Write descriptions that help the LLM understand:

What the tool does
When to call it
What data it returns

Hints

The hints: block provides execution metadata that the runtime uses for optimization:

TOOLS:
  get_balance(account_id: string) -> {balance: number}
    description: "Get account balance"
    hints:
      cacheable: true
      latency: fast
      timeout: 5000

Hint	Type	Default	Description
`cacheable`	`boolean`	none	Whether results can be cached across calls with the same parameters
`latency`	`"fast"` \| `"medium"` \| `"slow"`	none	Expected latency category for runtime scheduling
`side_effects`	`boolean`	none	Whether the tool modifies external state
`requires_auth`	`boolean`	none	Whether the tool requires authenticated context
`timeout`	`number`	none	Tool-specific timeout in milliseconds (overrides `EXECUTION.tool_timeout`)

HTTP tools

HTTP tools call REST API endpoints. They are the most common tool type.

TOOLS:
  search_flights(origin: string, destination: string, date: date) -> {flights: {id: string, price: number}[]}
    description: "Search available flights"
    type: http
    endpoint: "https://api.flights.com/v1/search"
    method: POST
    auth: bearer
    timeout: 10000
    retry: 3
    retry_delay: 1000

HTTP binding properties

Property	Type	Required	Default	Description
`type`	`"http"`	Yes	—	Declares this as an HTTP tool
`endpoint`	`string`	Yes	—	URL or path for the API call. Supports path parameters: `"/hotels/{hotel_id}"`
`method`	`"GET"` \| `"POST"` \| `"PUT"` \| `"PATCH"` \| `"DELETE"`	Yes	—	HTTP method
`auth`	`string`	No	`"none"`	Authentication type (see Auth)
`timeout`	`number`	No	`EXECUTION.tool_timeout`	Request timeout in milliseconds
`retry`	`number`	No	none	Number of retry attempts on failure
`retry_delay`	`number`	No	none	Delay in milliseconds between retries
`headers`	`Record<string, string>`	No	none	Custom HTTP headers
`query_params`	`Record<string, string>`	No	none	Query string parameters
`body_template`	`string`	No	none	Custom body template with interpolation
`rate_limit`	`number`	No	none	Maximum requests per second
`circuit_breaker`	`{threshold, resetMs}`	No	none	Circuit breaker configuration

Path parameters

Use curly braces in the endpoint to reference tool parameters:

TOOLS:
  get_hotel(hotel_id: string) -> Hotel
    type: http
    endpoint: "/hotels/{hotel_id}"
    method: GET

Headers

Custom headers are specified as key-value pairs:

TOOLS:
  get_data(query: string) -> {results: object[]}
    type: http
    endpoint: "/api/data"
    method: POST
    headers:
      X-Api-Version: "2024-01"
      Accept: "application/json"

Auth

The auth: property specifies the authentication mechanism. The runtime resolves credentials from the project’s credential store — the ABL document never contains actual secrets.

Auth type	Description
`none`	No authentication
`bearer`	Bearer token in `Authorization` header
`api_key`	API key (header name configurable via `auth_config`)
`oauth2_client`	OAuth 2.0 client credentials flow
`oauth2_user`	OAuth 2.0 authorization code flow (user-scoped tokens)
`saml`	SAML assertion-based authentication
`custom`	Custom authentication with configurable headers

Auth configuration

For auth types that require additional configuration, use the auth_config: block:

TOOLS:
  get_user_data(user_id: string) -> {name: string, email: string}
    type: http
    endpoint: "/api/users/{user_id}"
    method: GET
    auth: oauth2_client
    auth_config:
      token_url: "https://auth.example.com/oauth/token"
      client_id: "my-client-id"
      client_secret: "{{secrets.OAUTH_CLIENT_SECRET}}"
      scopes: "read:users"

TOOLS:
  call_partner_api(payload: string) -> {status: string}
    type: http
    endpoint: "https://partner.example.com/api"
    method: POST
    auth: api_key
    auth_config:
      header_name: "X-API-Key"

Auth config property	Type	Used with	Description
`token_url`	`string`	`oauth2_client`, `oauth2_user`	OAuth token endpoint URL
`client_id`	`string`	`oauth2_client`, `oauth2_user`	OAuth client identifier
`client_secret`	`string`	`oauth2_client`, `oauth2_user`	OAuth client secret (use `{{secrets.X}}` placeholders)
`scopes`	`string`	`oauth2_client`, `oauth2_user`	Space-separated OAuth scopes
`header_name`	`string`	`api_key`	Custom header name for the API key
`provider`	`string`	`oauth2_user`, `saml`	Auth provider identifier
`custom_headers`	`Record<string, string>`	`custom`	Custom authentication headers

Secret placeholders

Credentials use {{secrets.NAME}} placeholder syntax. The runtime resolves these from the project’s secret store at execution time. Never embed actual credentials in ABL files.

auth_config:
  client_secret: "{{secrets.PARTNER_OAUTH_SECRET}}"

Result transformation

Tool results are available in the session context after execution. You can map specific result fields to session variables using on_result: and handle errors with on_error::

TOOLS:
  get_balance(account_id: string) -> {balance: number, currency: string}
    description: "Get account balance"
    type: http
    endpoint: "/api/balance"
    method: GET
    on_result:
      set:
        current_balance: result.balance
        account_currency: result.currency
    on_error:
      set:
        balance_error: error.message

SSRF protection

The platform enforces SSRF (Server-Side Request Forgery) protection on all HTTP tool endpoints. Private IP ranges, localhost, and internal network addresses are blocked at the runtime level. Only allowlisted domains and public endpoints are permitted for HTTP tool calls.

Circuit breaker

The circuit breaker prevents cascading failures by halting requests to a failing endpoint after a threshold of consecutive errors:

TOOLS:
  unreliable_api(query: string) -> {data: string}
    type: http
    endpoint: "https://api.example.com/data"
    method: GET
    circuit_breaker:
      threshold: 5
      resetMs: 30000

Property	Type	Description
`threshold`	`number`	Number of consecutive failures before the circuit opens
`resetMs`	`number`	Milliseconds to wait before trying the endpoint again

MCP tools

MCP (Model Context Protocol) tools connect to external MCP servers that expose tools dynamically. The runtime handles protocol negotiation, transport, and tool discovery.

TOOLS:
  web_search(query: string) -> {results: {title: string, url: string, snippet: string}[]}
    description: "Search the web"
    type: mcp
    server: "brave-search"

MCP binding properties

Property	Type	Required	Default	Description
`type`	`"mcp"`	Yes	—	Declares this as an MCP tool
`server`	`string`	Yes	—	MCP server name (resolved from runtime configuration)
`server_tool`	`string`	No	Tool name	Tool name on the MCP server (if different from the ABL tool name)

Server configuration

The server value is a logical name that maps to an MCP server configuration in the project’s runtime settings. Server configuration (transport type, connection URL, authentication) is managed at the project level, not in the ABL file. The platform supports these MCP transport types:

Transport	Description
`stdio`	Standard input/output (for local MCP server processes)
`http`	HTTP-based transport (Streamable HTTP)
`websocket`	WebSocket-based transport

Dynamic tool discovery

MCP servers can expose multiple tools. When you declare an MCP tool in ABL, you bind a specific tool from the server. If the tool name on the MCP server differs from the tool name in your ABL file, use server_tool: to specify the server-side name:

TOOLS:
  search(query: string) -> {results: object[]}
    description: "Search using Brave"
    type: mcp
    server: "brave-search"
    server_tool: "brave_web_search"

Code tools (sandbox)

Code tools execute user-provided JavaScript or Python code in an isolated sandbox environment with resource limits and no network access.

TOOLS:
  calculate_tax(income: number, state: string) -> {tax: number, rate: number}
    description: "Calculate state income tax"
    type: sandbox
    runtime: javascript
    timeout: 5000
    memory_mb: 128
    code: |
      const rates = { CA: 0.133, NY: 0.109, TX: 0 };
      const rate = rates[state] || 0.05;
      return { tax: income * rate, rate };

Sandbox binding properties

Property	Type	Required	Default	Description
`type`	`"sandbox"`	Yes	—	Declares this as a sandbox tool
`runtime`	`"javascript"` \| `"python"`	Yes	—	Execution runtime
`code`	`string`	No	none	Inline source code (pipe block syntax for multi-line)
`timeout`	`number`	No	Platform default	Maximum execution time in milliseconds
`memory_mb`	`number`	No	Platform default	Memory limit in megabytes

Isolation

Sandbox tools execute in a gVisor-isolated environment with the following restrictions:

No network access
No filesystem access beyond the sandbox working directory
Resource limits enforced (CPU, memory, execution time)
Each execution runs in a fresh environment

JavaScript runtime

JavaScript code tools have access to standard JavaScript built-ins. The code should return a value matching the declared return type.

TOOLS:
  format_currency(amount: number, currency: string) -> {formatted: string}
    type: sandbox
    runtime: javascript
    code: |
      const formatter = new Intl.NumberFormat('en-US', {
        style: 'currency',
        currency: currency
      });
      return { formatted: formatter.format(amount) };

Python runtime

Python code tools use a sandboxed Python interpreter. The code should return a dictionary matching the declared return type.

TOOLS:
  analyze_text(text: string) -> {word_count: number, sentences: number}
    type: sandbox
    runtime: python
    code: |
      import re
      words = len(text.split())
      sentences = len(re.split(r'[.!?]+', text))
      return {"word_count": words, "sentences": sentences}

Lambda tools

Lambda tools invoke cloud serverless functions. The function name is a logical identifier resolved to an actual endpoint (ARN, URL) at runtime through the project’s function registry.

TOOLS:
  process_document(document_url: string, format: string) -> {text: string, pages: number}
    description: "Extract text from a document"
    type: lambda
    function: "document-processor"
    runtime: "nodejs20"
    timeout: 30000

Lambda binding properties

Property	Type	Required	Default	Description
`type`	`"lambda"`	Yes	—	Declares this as a lambda tool
`function`	`string`	Yes	—	Logical function name (resolved at runtime)
`runtime`	`string`	No	none	Runtime hint (e.g., `"nodejs20"`, `"python3.12"`)
`timeout`	`number`	No	Platform default	Override timeout for this function in milliseconds

Async webhook tools

Async webhook tools send an HTTP request with a callback URL injected into the payload. The external system processes the request asynchronously and posts the result back to the callback URL when complete.

TOOLS:
  generate_report(report_type: string, date_range: string) -> {report_url: string, status: string}
    description: "Generate a financial report (processed asynchronously)"
    type: async_webhook
    endpoint: "https://reports.internal/api/generate"
    method: POST
    callback_url_field: "callbackUrl"
    timeout_seconds: 3600

Async webhook binding properties

Property	Type	Required	Default	Description
`type`	`"async_webhook"`	Yes	—	Declares this as an async webhook tool
`endpoint`	`string`	Yes	—	URL to send the initial request
`method`	`"POST"` \| `"PUT"` \| `"PATCH"`	Yes	—	HTTP method
`headers`	`Record<string, string>`	No	none	Custom HTTP headers
`callback_url_field`	`string`	No	`"callbackUrl"`	Dot-path in the request body where the callback URL is injected
`timeout_seconds`	`number`	No	`3600`	Timeout in seconds for the async callback response

Tool file imports

Tool definitions can be organized into reusable .tools.abl files and imported into agent documents. This allows sharing tool definitions across multiple agents.

Tool file format

A .tools.abl file starts with a TOOLS: section that can include shared defaults:

TOOLS:
  base_url: "https://api.hotels.com/v1"
  auth: bearer
  timeout: 5000
  retry: 3

  search_hotels(destination: string, checkin: date, checkout: date) -> Hotel[]
    type: http
    endpoint: "/search"
    method: POST
    description: "Search available hotels"

  get_hotel(hotel_id: string) -> Hotel
    type: http
    endpoint: "/hotels/{hotel_id}"
    method: GET
    description: "Get hotel details by ID"

Shared defaults

The following defaults can be set at the top of a .tools.abl file and apply to all tools in the file:

Default	Type	Description
`base_url`	`string`	Base URL prepended to all relative endpoint paths
`auth`	`string`	Default auth type for all tools
`timeout`	`number`	Default timeout in milliseconds
`retry`	`number`	Default retry count
`retry_delay`	`number`	Default retry delay in milliseconds
`rate_limit`	`number`	Default rate limit (requests per second)
`headers`	`Record<string, string>`	Default headers applied to all tools

Import syntax

Import tools from a .tools.abl file into an agent using the file: directive within the TOOLS: section:

TOOLS:
  file: "./tools/hotels-api.tools.abl" [search_hotels, get_hotel]

The import specifies:

The path to the .tools.abl file (relative to the agent file)
An optional list of specific tool names to import (in brackets). If omitted, all tools from the file are imported.

Example

Given the file tools/hotels-api.tools.abl:

TOOLS:
  base_url: "https://api.hotels.com/v1"
  auth: bearer

  search_hotels(destination: string, checkin: date, checkout: date) -> Hotel[]
    type: http
    endpoint: "/search"
    method: POST
    description: "Search available hotels"

  get_hotel(hotel_id: string) -> Hotel
    type: http
    endpoint: "/hotels/{hotel_id}"
    method: GET
    description: "Get hotel details by ID"

  get_hotel_reviews(hotel_id: string, limit: number = 10) -> Review[]
    type: http
    endpoint: "/hotels/{hotel_id}/reviews"
    method: GET
    description: "Get reviews for a hotel"

An agent file can import selected tools:

AGENT: Hotel_Search

TOOLS:
  file: "./tools/hotels-api.tools.abl" [search_hotels, get_hotel]

  # Additional agent-specific tools
  check_availability(hotel_id: string, dates: string) -> {available: boolean}
    description: "Check real-time availability"
    type: http
    endpoint: "/api/availability"
    method: POST

Tool features

Confirmation

The confirmation: block configures whether the agent should ask the user for confirmation before executing a tool. This is particularly important for tools with side effects (e.g., executing a payment, deleting a record).

TOOLS:
  execute_payment(amount: number, recipient: string) -> {confirmation_id: string}
    description: "Execute a payment"
    type: http
    endpoint: "/api/payments"
    method: POST
    confirmation:
      require: always
      immutable_params: [recipient]

Property	Type	Default	Description
`require`	`"always"` \| `"never"` \| `"when_side_effects"`	none	When to require user confirmation
`immutable_params`	`string[]`	none	Parameters that cannot be changed after confirmation

Caching hints

Use the cacheable hint to indicate that a tool’s results can be cached:

TOOLS:
  get_exchange_rate(from: string, to: string) -> {rate: number}
    description: "Get current exchange rate"
    type: http
    endpoint: "/api/fx/rate"
    method: GET
    hints:
      cacheable: true
      latency: fast

When cacheable: true, the runtime may cache results for identical parameter combinations. When cacheable: false, results are never cached (use this for tools that return time-sensitive data).

PII access

The pii_access: property declares what level of personally identifiable information (PII) a tool can access:

TOOLS:
  verify_identity(ssn_last4: string, dob: string) -> {verified: boolean}
    description: "Verify customer identity"
    type: http
    endpoint: "/api/identity/verify"
    method: POST
    pii_access: user

Value	Description
`tools`	Tool can access PII data from other tool results
`user`	Tool can access user-provided PII
`logs`	PII from this tool may appear in logs
`llm`	PII from this tool is sent to the LLM

Context access

The context_access: block declares which session context variables a tool reads from and writes to. This enables the runtime to automatically inject context into HTTP requests and apply result values back to session state:

TOOLS:
  update_profile(name: string) -> {updated: boolean}
    description: "Update user profile"
    type: http
    endpoint: "/api/profile"
    method: PUT
    context_access:
      read: [user.id, user.email]
      write: [user.name, user.updated_at]

Store result

The store_result: property controls whether the raw tool result blob is stored in the session context. Defaults to true.

TOOLS:
  log_event(event: string) -> {logged: boolean}
    description: "Log an audit event"
    type: http
    endpoint: "/api/audit"
    method: POST
    store_result: false

Language overview — file structure and syntax
Agent declaration — tool_timeout and model settings in EXECUTION
GATHER — information collection (often used alongside tools)
FLOW — CALL action for invoking tools within flow steps

API Reference

ABL Reference

CLI Reference

SDK

Documentation Index

​Tools

​Tool declaration syntax

​Signature format

​Parameter syntax

​Parameter types

​Object parameters

​Array parameters

​Return type

​Description

​Hints

​HTTP tools

​HTTP binding properties

​Path parameters

​Headers

​Auth

​Auth configuration

​Secret placeholders

​Result transformation

​SSRF protection

​Circuit breaker

​MCP tools

​MCP binding properties

​Server configuration

​Dynamic tool discovery

​Code tools (sandbox)

​Sandbox binding properties

​Isolation

​JavaScript runtime

​Python runtime

​Lambda tools

​Lambda binding properties

​Async webhook tools

​Async webhook binding properties

​Tool file imports

​Tool file format

​Shared defaults

​Import syntax

​Example

​Tool features

​Confirmation

​Caching hints

​PII access

​Context access

​Store result

​Related