create_spec_for_function
Generate a functional-requirements spec (.3tg.md) scoped to a single exported function or React component. Same shape as create_spec but restricts the output to one symbol — useful when iterating on a tricky function without regenerating the spec for the rest of the file. IMPORTANT — never hand-a...
This record as markdown: /tools/dev-3tg-mcp/create-spec-for-function.md
What create_spec_for_function does on 3TG Test Generation
AI agents use create_spec_for_function to create or update resources in 3TG Test Generation, usually the action step of a workflow, after the agent has gathered context. Every call changes real data in your 3TG Test Generation environment.
| Parameter | Type | Required | Description |
|---|---|---|---|
clientId | string | Yes | The 3tg.dev client ID. |
fileName | string | Yes | Path of the source file relative to the user's project root. |
settings | object | — | Subset of .3tg/settings.json relevant to this tool. |
cliConfig | object | — | Optional per-request 3TG CLI config. The agent assembles this from TWO disk locations and merges them (per-source wins on conflict) before forwarding the merged |
moduleType | string | — | Optional Node module type of the consumer project — the value of the `type` field in the project root's `package.json`. The agent reads that one field (only) an |
sourceCode | string | Yes | Full UTF-8 contents of the source file. |
functionName | string | Yes | Name of the exported function or React component to scope the spec to. Forwarded to 3TG as `-f <functionName>`. Use `default` for default exports. |
Parameters from the server's own tool schema.
Why create_spec_for_function is rated Medium
The tool creates or generates a specification document scoped to a function or component. While it produces structured output that gets written to a file, the operation is reversible (specs can be regenerated or deleted), there are no side effects on external systems, no code execution occurs, and no data is destructively modified.
From the tool's definition Tool generates and creates a functional-requirements spec file (`.3tg.md`). The description states it generates output and the name contains `create_`. This is a content generation tool that produces new files/specifications.
Risk signalsAccepts file system path (fileName) · High parameter count (12 properties) · Admin/system-level operation
Attacks that exploit this kind of access
The rule that runs create_spec_for_function safely
PolicyLayer is an MCP gateway: it sits between your AI agents and 3TG Test Generation, and checks every tool call against a rule you set before the call runs. Nothing changes on the server itself. For create_spec_for_function, this is the rule to start with:
create_spec_for_function stays usable, but capped: an agent stuck in a loop can't make hundreds of changes a minute. Everything else on the server is denied unless you say otherwise.
The button opens the PolicyLayer dashboard: create your workspace, connect 3TG Test Generation, apply this rule, and every create_spec_for_function call is checked against it from then on.
Questions about create_spec_for_function
Generate a functional-requirements spec (.3tg.md) scoped to a single exported function or React component. Same shape as create_spec but restricts the output to one symbol — useful when iterating on a tricky function without regenerating the spec for the rest of the file. IMPORTANT — never hand-author a .3tg.md yourself. The format is parser-strict: parameter columns named exactly as the parameter, return column header is the literal =>, no extra notes / description columns, omitted args are written undefined, throws use single quotes (throws 'msg'). Always call this tool to emit the scaffold; the user can then edit rows. Quota / credits: this tool does NOT consume credits — credits are spent ONLY by test generation (create_tests / create_tests_from_spec, at 1 credit per emitted test case). Spec generation is free. CRITICAL POST-CALL ACTION — write returned files to disk: The MCP server does NOT touch the user's filesystem. It returns the generated file CONTENTS in the response's files array. After this tool returns, you MUST iterate over files and write each entry's content verbatim to its path using your native file-write capability (e.g. Write / edit_file / create_file — whatever your client exposes). Create parent directories as needed. Returned paths are project-root-relative and already translated to the .3tg/ mirror convention where applicable (e.g. specs land under .3tg/<source-path>.3tg.md; tests / mocks travel through unchanged). Write each path verbatim. Do NOT claim "Generated test file: <path>" unless you have actually written the file. The user will assume the MCP wrote it and waste time looking for a non-existent file. If you can't write for some reason (permission denied, no write capability in this client), return the contents inline in your message so the user can copy-paste them. Never report success silently when the write didn't happen. It is categorised as a Write tool in the 3TG Test Generation MCP Server, which means it can create or modify data. Consider rate limits to prevent runaway writes.
create_spec_for_function accepts 7 parameters: clientId, fileName, settings, cliConfig, moduleType, sourceCode, functionName. Required: clientId, fileName, sourceCode, functionName. The full parameter table on this page comes from the server's own tool schema.
Register the 3TG Test Generation MCP server in PolicyLayer and add a rule for create_spec_for_function: allow, deny, rate-limit, or require approval. Point your MCP client at the PolicyLayer proxy URL and the rule is enforced on every call, before it reaches 3TG Test Generation. Nothing to install.
create_spec_for_function is a Write tool with medium risk. Write tools should be rate-limited to prevent accidental bulk modifications.
Yes. Add a rate_limit block to the create_spec_for_function rule in your PolicyLayer policy. For example, setting max: 10 and window: 60 limits the tool to 10 calls per minute. Rate limits are tracked per agent session and reset automatically.
Set action: deny in the PolicyLayer policy for create_spec_for_function. The AI agent will receive a policy violation error and cannot call the tool. You can also include a reason field to explain why the tool is blocked.
create_spec_for_function is provided by the 3TG Test Generation MCP server (https://mcp.3tg.dev/mcp). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.
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