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

Adds real behavioral context beyond the annotations: it verifies the stored object against what was signed on size and content-type before marking the attachment ready, and describes the returned snapshot including public variant URLs. Idempotency is repeated from idempotentHint but is made concrete ('returns the same snapshot'). It stops short of saying what happens on a verification mismatch or whether any auth/ownership check applies.

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?

Four short sentences, front-loaded with the action and its precondition, then behavior, then return value, then idempotency. Every sentence carries distinct information with no filler.

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 mutation tool with no output schema, it covers the precondition, the verification behavior, the return shape, and idempotency. The remaining gap is failure semantics (what a size/content-type mismatch produces) and permission requirements, which an agent would need to handle errors correctly.

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?

With a single parameter at 100% schema coverage, the schema already documents attachment_id as the ULID from sign_attachment_upload and states the PUT precondition. The description restates essentially the same information, adding no format, validation, or edge-case detail beyond it, so the baseline of 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+resource ('Finalize/confirm an out-of-band upload') and places it precisely in the workflow after the bytes have been PUT to the presigned URL. This distinguishes it cleanly from the sibling sign_attachment_upload, which produces the URL and id rather than finalizing.

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?

Gives explicit sequencing guidance: confirm only after the file bytes have been successfully PUT to the presigned URL, and it names the source of the id (sign_attachment_upload). It does not state any when-not conditions (e.g., what to do if the upload failed or the object was already confirmed outside the tool), so it stops short of full routing guidance.

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