index_stats

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

With no annotations, the description carries the burden of behavioral disclosure. It explains what the tool reports, including size, coverage, resolution breakdown, and indexed_at, and adds diagnostic meaning beyond a simple field list. It does not explicitly state that the tool is read-only, but for a stats tool this is strongly implied by the content described.

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 compact and front-loaded: the first sentence states exactly what the tool reports, and the second sentence gives actionable usage guidance. Every sentence earns its place with no 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 zero-parameter tool with an output schema available, the description provides everything needed to decide when and how to use it. It explains the tool's purpose, the data it returns, and the diagnostic scenario in which it is useful, leaving no meaningful gap.

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?

The tool takes zero parameters, so there are no parameter meanings to clarify. The description still adds conceptual value by naming the key output dimensions (size, coverage, edge-resolution breakdown, indexed_at), which is appropriate for a parameterless tool.

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 clearly identifies the resource and content ('Index health: size, coverage, and the edge-resolution breakdown by rule'), which immediately distinguishes it from the symbol-focused sibling tools. However, it lacks an explicit verb like 'reports' or 'returns', so it falls just short of the strongest purpose clarity.

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 an explicit trigger: 'Worth a call when graph answers look thin'. It also explains how to interpret results ('low resolution rate or a stale indexed_at tells you the index needs rebuilding rather than the code being unusual'), which is excellent practical guidance for when this tool is the right choice.

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