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

Annotations already provide readOnlyHint and idempotentHint, so the bar is lower. The description adds useful behavior beyond annotations: authentication requirements for download URLs, signed URL expiry, and the fact that the tool returns metadata rather than raw bytes. No contradiction.

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?

Three short sentences with no filler. The purpose is front-loaded, followed by actionable download/auth guidance, then a clear boundary. Every sentence 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 simple read-only metadata tool with full schema coverage and readOnly/idempotent annotations, the description covers purpose, download mechanics, auth, expiry, and exclusions. It does not enumerate metadata fields, but that is a minor gap for this tool's simplicity.

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 coverage is 100%, so file_id and token are already documented. The Bearer/signed-URL mention adds context about how tokens are used, but it is more about returned download URLs than the input parameters themselves.

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 'File metadata and how to read it,' which identifies the resource and scope, and it explicitly warns not to ask for file bytes. It lacks an explicit imperative verb like 'retrieves,' but the tool name and title make the purpose unambiguous.

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 gives concrete download instructions: use download_url with Bearer or signed_download_url without a token, and notes the 1-hour validity. It also states a clear exclusion: do not ask this tool to dump file bytes. It does not name sibling tools as alternatives, but the guidance is actionable.

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