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Functions and tools

Code tool

Run your own JavaScript in a sandbox during a call, with access to the arguments, dynamic variables, call metadata and a guarded fetch.

The Code function (type: "code") runs JavaScript you write, in a sandbox on the Tried API. Use it for small logic that does not justify hosting an endpoint: date maths, formatting, routing decisions, or a quick call to a public API with fetch.

How it runs#

The code is the body of an async function. Whatever it returns is the result. Three values are in scope:

Name Contents
args The arguments the LLM passed, shaped by your parameters schema
dv All dynamic variables of the call as strings (defaults, request variables, collected values, system variables such as current_time)
metadata The call's metadata object

fetch(url, init) is available and returns an object with status, ok, headers, text() and json(). console.log output is captured by the sandbox (up to 200 lines) but is not passed to the LLM.

// args, dv (dynamic variables) and metadata are in scope
const total = Number(args.items) * Number(dv.unit_price || 0);
const res = await fetch(`https://api.example.com/postcodes/${encodeURIComponent(args.postcode)}`);
const area = res.ok ? (await res.json()).region : "unknown";
return { total, area, eligible: total > 100 && area !== "unknown" };

The returned value is serialised to JSON, cut to 15,000 characters and handed to the LLM. With Speak after execution on (the default), the agent then replies.

Configure in the dashboard#

  1. Open the agent, expand Functions, click Add and choose Code.
  2. Name and Description. The default description is "Run JavaScript and return a result."
  3. JavaScript: your code. Save is disabled while it is empty.
  4. Parameters: the arguments the LLM fills in (Form or JSON schema).
  5. Timeout (seconds): 5 to 60. Default 10.
  6. Response variables: name to JSON path, for example total to $.total.
  7. While it runs options, then Save.

Fields#

Field Type Default Description
type "code"
name, description string
code string, up to 20,000 characters Body of an async function
parameters JSON schema object Arguments for the LLM
timeout_ms integer, 1,000 to 60,000 10,000 Total run time
response_variables object of name to JSON path Saved from the returned value
speak_during_execution, speak_after_execution, execution_message_description See execution options

Sandbox limits#

Limit Value
Engine QuickJS compiled to WebAssembly, no access to the host process, file system or environment
Memory 32 MB
Stack 1 MB
Run time timeout_ms, capped by the API setting CODE_SANDBOX_MAX_MS (default 60,000 ms)
fetch http and https only, 15 s per request, response body cut to 200,000 characters
fetch destinations Private network addresses (10/8, 127/8, 0/8, 169.254/16, 172.16/12, 192.168/16, 100.64/10, IPv6 loopback, fc, fd and fe80 prefixes) are refused
Result 15,000 characters of JSON

SANDBOX_ALLOW_PRIVATE_NETWORK=1 on the API lifts the private network check for local development.

Errors#

Situation Text the LLM gets
Your code throws or a promise rejects Error: <message>
Syntax error Error: <message>
Over the time limit Error: Code timed out after <ms> ms while waiting on a promise. A busy loop is stopped by the interrupt handler and returns an Error: interrupted style message
Code ends with a pending promise and no return Error: Code finished without a result (unresolved promise)
API unreachable Error: code sandbox unreachable: ...

return nothing and the result is null.

Response variables#

response_variables reads from the returned value with the same JSON path syntax as custom functions ($.a.b[0]). With the example above, {"eligible": "$.eligible"} saves {{eligible}} as true or false for the rest of the call.

In conversation flows#

The code node runs code at a fixed step without an LLM call, stores result fields as variables and then follows equation edges. It is the usual way to branch on computed values.

Gotchas#

  • Node.js APIs such as require, process and Buffer are not available. Keep code self-contained.
  • dv values are strings. Convert with Number() before maths.
  • The sandbox runs on the API, so fetch goes out from the API host, not the voice worker.
Code nodeRun code at a fixed step of a flow.Custom functionCall your own endpoint instead.