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

The description goes well beyond the annotations by disclosing conditional behavior: site ids produce a readable summary with specific fields, file ids return UTF-8 text only for text types at most 1 MB, otherwise a short note pointing to the live URL. It also states the return shape. This is rich behavioral context consistent with the readOnly and idempotent annotations.

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 core purpose appears in the first sentence, followed by terse, high-value detail for each id form. Every sentence contributes useful information without redundancy.

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 single-parameter read-only tool with annotations covering safety and idempotence, the description is complete. It covers both id forms, conditional behavior, output shape, and even the fallback for non-text or oversized files. An agent has everything needed to invoke it correctly.

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?

Although schema coverage is 100%, the description adds substantial meaning beyond the schema. It explains exactly what each id form yields, including the summary fields and the file-size/type condition. This lets an agent predict output behavior from the parameter value alone.

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: 'Fetch one search result by id.' It then details the two id forms ('site:<site_id>' and 'file:<site_id>:<path>') and what each returns, making the tool's purpose unmistakable. This clearly distinguishes it from search (which returns results) and from other site/file tools.

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 clearly establishes the context for use: after search has returned an id, use fetch to retrieve that specific result. It does not explicitly name alternative tools or exclusions, but the id-returned-by-search framing gives clear contextual guidance.

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