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

Annotations already declare readOnlyHint, idempotentHint, destructiveHint=false and openWorldHint=false, so the safety profile is fully covered without the description. The description's one extra contribution is scoping the return to metadata rather than document content, but it says nothing about behavior on a missing id or any permission requirements.

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 tight sentence with the action verb first and the key parameter named at the end. No filler, though it is brief enough that one more clause of routing guidance would have fit without bloat.

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 one-parameter read with no output schema, an agent still lacks the shape of the returned metadata and the error semantics for an unknown id. Safety behavior is fully delegated to annotations, so the remaining gaps are modest but real.

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 0%, so the description has to carry the load; it explains that fileId identifies 'an existing Files document or folder', which is genuinely useful since the schema's uuid pattern does not reveal that both files and folders are addressable. It still does not say where such an id comes from or what the format looks like in prose.

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 ('Retrieve') and resource ('metadata for an existing Files document or folder'), and the word 'metadata' implicitly separates it from read_file (content) and list_files (enumeration). It does not however explicitly name those siblings, so the differentiation is inferred rather than stated.

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 'by fileId' implies the precondition that the caller already holds an id, and 'existing' hints that this is a lookup rather than a create. There is no explicit when-to-use versus read_file or list_files guidance and no stated failure behavior for a stale or unknown id.

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