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

Annotations already declare the safe read-only, idempotent, non-destructive profile, so the bar is lower. The description contributes genuinely new behavior: the signed URL expires after 1 hour and the result is a GCS URL openable by the model or external tools, whereas the operation's `file_url` needs Markifact authentication. It does not discuss failure modes or retry behavior, but the ambiguity error is already documented in the schema.

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?

Front-loaded with the core purpose and well organized into purpose, when-to-use, contrast, and return. The closing sentence 'Returns a signed GCS URL for the file' restates the opening line rather than adding information, a small 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?

With an output schema present, return values need no elaboration, and annotations carry the safety profile. What remains — purpose, when to use it versus the authenticated `file_url`, and the 1-hour expiry — is fully covered for a single-parameter 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?

Schema description coverage is 100% and the schema already explains that a full filename with extension is expected and that extensionless prefixes can trigger an ambiguity error. The description adds no syntax or format detail beyond what the schema provides, so baseline 3 applies.

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 and resource — 'Get a signed URL for a private file' — and immediately distinguishes its output from the 'file_url' values that appear on operations. An agent can tell it apart from siblings like read_file or upload_media without opening a schema.

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?

Explicitly says when to reach for it ('when an operation returns a `file_id` and you need a temporary, directly accessible URL') and contrasts it with the authenticated user-facing `file_url` values. The alternative is named and the condition that selects this tool over it is stated, leaving nothing to inference.

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