File outline

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

Annotations already declare readOnlyHint=true and openWorldHint=false, so the safety profile is covered. The description adds useful behavioral detail beyond that: it reports line ranges, limits scope to a single file, and lists the symbol kinds returned, which helps set expectations about output granularity.

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?

Two sentences with no wasted words. The core action and scope are front-loaded, the symbol list is compact but complete, and the value proposition ('cheaper than reading the whole file') earns its place.

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 read-only single-file listing tool with fully documented parameters, the description is largely complete: it tells the agent what will be listed and why it should be used. It does not describe the exact return format or failure modes, but those are minor given the tool's simplicity and the readOnlyHint annotation.

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%: both 'file' and 'path' have clear descriptions ('relative to the repository root' and 'absolute path to the repository root'). The tool description adds no parameter-level meaning, so the baseline of 3 applies.

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 and resource: 'List the structure of one JavaScript/TypeScript file.' It enumerates exactly what is included (functions, classes with methods, interfaces, types, enums, constants, line ranges), and 'one file' clearly differentiates it from repository-wide tools like repo_map or entry_points.

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 phrase 'when you only need its shape' provides a clear use case, and 'cheaper than reading the whole file' gives the agent a cost-based decision signal. It does not explicitly name sibling tools or state when not to use it, so it stops short of a 5.

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