run_tests

Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?

Beyond the sparse annotation (readOnlyHint=false), the description reveals the compiled safety envelope: fixed argv, no shell interpolation, 120s timeout, 64KB output cap per stream. It also notes the Shell-exec pilot status and details the return fields, providing substantial behavioral context that annotations alone do not convey.

Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

Is the description appropriately sized, front-loaded, and free of redundancy?

Four dense sentences front-load the core action and safety constraints, then proceed to restrictions, parameter guidance, and return fields. Every sentence contributes new information with no repetition or filler.

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

For a tool with two optional parameters and no output schema, the description covers purpose, safety envelope, supported/unsupported runners, parameter usage, and return value shape. The only minor omission is an explicit statement that passing neither parameter runs the full suite, but this is strongly implied by 'narrow the run.'

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

Although the input schema already describes both parameters, the description adds mapping: `filter` maps to vitest --testNamePattern and `path` is an in-tree file/directory, clarifying exact usage. This goes beyond the schema's generic descriptions and helps an agent choose parameters correctly.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Does the description clearly state what the tool does and how it differs from similar tools?

The description opens with a specific verb+resource: 'Run the consumer project's vitest test suite,' clearly identifying the tool's action and scope. It further distinguishes itself by stating it supports only vitest projects and that other runners return an error, making it unmistakable from a generic test runner.

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Does the description explain when to use this tool, when not to, or what alternatives exist?

The description gives explicit exclusions ('other runners ... return an error until a future council round approves them') and explains how to narrow runs with `filter` or `path`. However, it does not name an alternative tool to use for non-vitest projects, so it stops short of full when-to-use-vs-alternative guidance.

Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.