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

Annotations cover the safety profile (readOnly=false, destructive=false, idempotent=false), and the description adds real substance beyond them: it verifies the object landed and matches declared size/sha256, and it explains that the file only becomes usable afterwards. The remaining gap is failure behavior — what happens if verification fails (error? partial object?) and whether re-invoking after a failed verify is safe, which matters given idempotentHint=false.

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 tight sentences, front-loaded with the action and its precondition, then the verification behavior, then the downstream usability, then a compact Returns line. With no output schema, the Returns enumeration earns its place rather than padding.

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 two-parameter, no-output-schema tool, the description supplies everything an agent needs: the prerequisite call, the PUT step between, the verification semantics, the return fields, and where the file_id becomes valid. Nothing material is left to inference.

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 file_id and in_workspace are already documented in the schema, and the description does not elaborate on either. It does add context that the sha256/size are checked against what was declared at upload-URL creation time, which clarifies why a mismatch matters, but that is not parameter-level detail. Baseline 3 applies when the schema does the heavy lifting.

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+resource (finish the file upload) and explicitly ties itself to its predecessor, files_create_upload_url, so the agent can place it in the upload lifecycle without opening a schema. It is clearly separable from the sibling files_upload / files_ingest / files_create_upload_url 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 precondition is unusually explicit: run it only after the bytes have been PUT to the upload_url from files_create_upload_url. It also routes the agent forward by naming messages_send, messages_send_email attachments, and documents.create as consumers of the resulting file_id. It does not, however, state when to prefer files_upload or files_ingest over this two-step flow, so the alternative-selection guidance is incomplete.

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