mavis_run_tests

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

With no annotations provided, the description carries the full burden of behavioral disclosure. It transparently states the output behavior ('Returns the full vitest output (truncated at 5MB)') and the pattern-filter behavior. It does not disclose potential side effects (e.g., tests modifying files), but for a test runner this is arguably implied. The truncation note is a valuable behavioral detail.

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?

The description is two sentences, front-loaded with the primary action, and every phrase adds value. It includes the action, scope, filtering option, output behavior, and use cases without unnecessary words.

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?

The tool has four parameters, no output schema, and no annotations. The description covers the main behavior, output format, and use cases. It does not explain each parameter, but the schema covers them. It could mention potential side effects or environment considerations, but for a focused test runner the description is sufficiently complete.

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?

Schema description coverage is 100%, so the schema already documents all four parameters. The description adds only a brief mention of the pattern filter, consistent with the schema. It does not elaborate on timeout, bail, or cwd beyond what the schema states, so the description provides no significant additional meaning. Baseline 3 is appropriate.

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 'Run vitest tests in the workspace', a specific verb+resource combination. It clearly distinguishes from sibling tools like git, bash, or search by focusing exclusively on test execution. The optional pattern filter and output note reinforce this dedicated purpose.

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 explicitly states when to use the tool: 'to verify a fix worked or to reproduce a failure.' This provides clear context for usage. It does not explicitly mention when not to use it or name alternative tools, which prevents a 5, but the given use cases are sufficient for a narrow tool.

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