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

Annotations only declare readOnlyHint=true, while the description adds that the URL is signed and time-limited and returns metadata. It does not state expiration duration or permission requirements, but it adds meaningful behavioral context beyond the annotation.

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?

A single efficient sentence with purpose front-loaded and no filler. Every element, including return type, file scope, and exclusion case, 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 URL-retrieval tool with no output schema, the description covers the return object (signed URL and metadata) and the use case. The optional entity parameter's effect is left to the schema, but nothing critical is missing.

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%, so the baseline is 3. The description says 'by fid' but adds no syntax or meaning beyond the schema, and it does not discuss the optional entity parameter.

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?

States a specific verb 'Returns' and resource 'signed, time-limited download URL and metadata for a file by fid', and scopes it to video, archives, and other non-inline files. This distinguishes it from sibling tools like file_get and file_info by explaining that it serves files not returned inline.

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?

Provides clear context: use for video, archives, and other files not returned inline. It implies file_get or file_info are alternatives for inline-accessible files, but does not explicitly name when not to use this tool.

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