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

Annotations already declare readOnlyHint=false, destructiveHint=false, and idempotentHint=false, so mutation is known. The description usefully adds that it creates both a video and per-recipient tracked links and returns them, but it does not warn about the non-idempotent behavior (re-running could create duplicate videos/links), which is the most consequential trait an agent needs here.

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?

Two tightly written sentences: the first front-loads the action sequence, the second states the return values. Nothing is wasted.

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 no output schema, the description helpfully enumerates the return payload (video, share link, recipient links), which is what an agent needs for downstream chaining. It stops short of covering retry/non-idempotency and the duration fallback condition ('unless Alto can measure the file') that the schema alone hints at.

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 71%, so the schema documents most parameters itself. The description adds meaning only for 'recipients' via 'one tracked link each', leaving uploadId, parts, title, duration, and slug to the schema — adequate but not compensating for the uncovered remainder.

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 three concrete actions (join parts, create the video, mint one tracked link per recipient) with a specific verb+resource, and explicitly ties itself to the sibling create_upload as the originating step. An agent can distinguish it from create_link, create_upload, and upload_video without opening any 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?

The phrase 'an upload started with create_upload' makes the prerequisite workflow clear, so an agent knows this is the terminating step of a multi-part upload. It does not, however, address when to prefer this over the create_link sibling for single-link cases, nor any failure/retry conditions.

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