outline

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

Beyond the annotations (readOnlyHint, idempotentHint, destructiveHint), the description discloses important behavioral nuances: the difference between 'not indexed' and 'defines nothing,' including the scenario of a file added since the last index build. It also describes the reply format in detail (one line per definition with name and line number), which is not captured by any structured field.

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?

Every sentence earns its place: purpose, alternative tool, path requirement, read-only mention, output format, and edge-case behavior. The description is front-loaded with the primary purpose and remains free of filler, despite the slight stylistic oddity of 'Code lane:'.

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?

With a single parameter, no output schema, and thorough annotations, this description covers everything an agent needs: what it does, how to invoke it, what the response looks like, and a critical edge case (not-indexed vs defines-nothing). The mention of the sibling tool where_used further completes the contextual picture.

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%, and the only parameter (path) is documented as 'Repository-relative path, exactly as the index stores it.' The description repeats 'repository-relative path' but adds no meaning beyond the schema. Since the schema already carries the full parameter documentation, the baseline of 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 states a specific verb and resource: 'lists what one file declares, in line order' and 'its shape without reading the whole thing.' It clearly distinguishes itself from the sibling tool where_used by naming which tool to use for an alternative goal. This leaves no ambiguity about what the tool does.

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 provides a routing condition: 'Use where_used instead to find every caller of one symbol.' It also clarifies the intended context of 'one file' and the repository-relative path requirement, making it clear when this tool is appropriate and when a sibling is better.

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