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

Beyond the read-only annotations, the description discloses important behavioral constraints: adapter fits must not be misrepresented as direct, unknown must not become does-not-fit, and results should be cited using the returned citation line and html_url. These are non-obvious output-handling rules that materially affect correct use.

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 front-loaded with the core list operation and follows with concise but necessary usage and output-handling constraints. Every sentence carries actionable information, with no redundant restatement of schema or annotations.

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 no output schema, the description explains the return structure enough for correct use: direct fits with footprint, adapter fits with plate chain, citation line, and html_url. It also covers the key caveat about absent optics, making it complete for this read-only lookup tool.

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 schema already has 100% description coverage, including the pistol slug/name format and the fit enum, so the description does not need to re-explain them. The description adds output semantics around direct/adapter fits but does not add parameter-specific guidance beyond the schema.

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: list optics with cited fits for one pistol, including direct/adapter distinctions. It is clear and actionable, but it does not explicitly name the sibling tools it differs from, such as check_fit or list_pistols_for_optic.

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?

It gives a concrete usage example ('what red dots fit my pistol') and clarifies that unlisted optics lack cited fit rather than proving non-fit. It does not explicitly say when to use check_fit or list_pistols_for_optic instead, so the alternative-routing guidance is implied rather than complete.

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