# validate_config

Validate a 3TG configuration object (.3tg.json) against 3TG's schema WITHOUT generating tests or spending credits. Use this whenever you or the user has hand-edited .3tg/config.3tg.json (or a per-source .3tg/<source>.md.3tg.json) — it catches the mistakes that would otherwise surface as confusing failures at generation time. WHAT IT CATCHES (via 3TG's -C check-config pass): - a value of the wrong type (e.g. mock-parameters set to a string instead of an object); - an unknown / misspelled key, including invalid rule names (e.g. rules.string.no-emppty or a no-such-rule); - any other Draft-7 schema violation. This complements the 3tg://schema/config resource: read that resource to discover the valid keys; call this tool to actively verify a concrete config before saving it. This tool is FREE — no clientId, no quota. On failure, problems lists the exact schema-violation lines 3TG reported; surface them to the user and help fix the config, then re-validate. A valid: true result means the config is structurally accepted by 3TG (it does not assert the values are semantically ideal for any particular source file).

Agent View of the PolicyLayer registry record for `validate_config`. HTML page: https://policylayer.com/tools/dev-3tg-mcp/validate-config

## Facts

- Tool: `validate_config`
- Server: 3TG Test Generation (`https://mcp.3tg.dev/mcp`) — https://policylayer.com/tools/dev-3tg-mcp.md
- Homepage: https://github.com/https://mcp.3tg.dev/mcp
- Risk category: Read (Low risk)
- Registry record: grade D, identity unverified
- Server auth posture: open
- Server rate-limited: no
- Parameters: 1 (1 required)
- Recommended policy verdict: Allowed

## Parameters

| Parameter | Type | Required | Description |
| --- | --- | --- | --- |
| `config` | object | yes | The parsed 3TG configuration object to validate — the JSON contents of `.3tg/config.3tg.json` or a `.md.3tg.json` file. The agent reads the file from disk, pars |

Parameters from the server's own tool schema.

## Example call (MCP tools/call, JSON-RPC 2.0)

```json
{
  "jsonrpc": "2.0",
  "id": 1,
  "method": "tools/call",
  "params": {
    "name": "validate_config",
    "arguments": {
      "config": {}
    }
  }
}
```

## Why validate_config is rated Low

This tool is a read-only validation/check operation. It examines a configuration file against a schema and reports errors without modifying files, executing code, or triggering test generation. It has no side effects—it purely retrieves and analyzes the structure of the configuration object to report validation results.

From the tool's own definition: "Tool description states it performs validation and checking WITHOUT generating tests or spending credits. The verb 'validate' combined with 'catches mistakes' indicates pure schema verification against a configuration object with no side effects, data…"

## Use case

AI agents call validate_config to retrieve information from 3TG Test Generation without modifying anything. It is typically the context-gathering step in research, monitoring, and reporting workflows, before the agent takes action elsewhere.

## Recommended policy (PolicyLayer)

Verdict: **Allowed**. Enforced by the PolicyLayer MCP gateway (https://policylayer.com/mcp-gateway) before a call reaches 3TG Test Generation:

```json
{
  "version": "1",
  "default": "deny",
  "tools": {
    "validate_config": {}
  }
}
```

## Other tools on 3TG Test Generation (9)

- `get_client_info` — Read — https://policylayer.com/tools/dev-3tg-mcp/get-client-info.md
- `help` — Read — https://policylayer.com/tools/dev-3tg-mcp/help.md
- `validate_spec` — Read — https://policylayer.com/tools/dev-3tg-mcp/validate-spec.md
- `create_agent_instructions` — Write — https://policylayer.com/tools/dev-3tg-mcp/create-agent-instructions.md
- `create_mock_for_function` — Write — https://policylayer.com/tools/dev-3tg-mcp/create-mock-for-function.md
- `create_spec` — Write — https://policylayer.com/tools/dev-3tg-mcp/create-spec.md
- `create_spec_for_function` — Write — https://policylayer.com/tools/dev-3tg-mcp/create-spec-for-function.md
- `create_tests` — Write — https://policylayer.com/tools/dev-3tg-mcp/create-tests.md
- `create_tests_from_spec` — Write — https://policylayer.com/tools/dev-3tg-mcp/create-tests-from-spec.md

## For agents

This record is a snapshot. Live verdicts and the full registry:

- Check every server in your MCP config at once: `npx -y policylayer stack`
- Vet a server before you add it: install the mcp-precheck skill — `npx skills add https://policylayer.com` (skill text: https://policylayer.com/skill.md)
- Query the registry over MCP: endpoint `https://api.policylayer.com/mcp` — tools `check_mcp_server`, `check_mcp_stack`, `check_tool`, `search_registry`, `get_change_events`

---

Source: the PolicyLayer MCP registry — one continuously verified record per MCP server. Full record: https://policylayer.com/registry?q=dev-3tg-mcp · API: https://policylayer.com/registry/api · Policy library: https://policylayer.com/policies/dev-3tg-mcp