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

Beyond the basic mutation implied by the annotations, the description discloses meaningful behaviors: the server assembles parts, verifies existence/size/magic bytes/storage quota, records the media file, mirrors finalize_media_upload's response shape, and automatically aborts on failed assembly. This is substantial context the annotations do not provide.

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 efficient sentences deliver the core behavior, verification steps, failure handling, response-shape reference, and usage condition. It is front-loaded with the primary action and contains 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 9-parameter mutation tool with no output schema, the description provides solid context: verification behavior, automatic abort, and a pointer to finalize_media_upload for response shape. It is slightly dependent on the agent knowing what finalize_media_upload returns, but otherwise the call context is adequately covered.

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 the parameters are already well documented. The description adds only a small touch by mentioning that parts must be collected with their ETags, but otherwise it does not deepen understanding of the individual parameters beyond what the schema states.

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?

The description clearly states the tool's verb and resource: it completes a chunked upload by assembling parts, verifying the stored object, and recording the media file. It references finalize_media_upload to position its behavior, though it does not explicitly state how it differs from that sibling beyond being the chunked variant.

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 description gives an explicit usage condition: 'Use this when all parts of a chunked upload are PUT and their ETags collected.' This is clear context for when to invoke the tool, though it does not explicitly mention when not to use it or name a specific alternative to prefer instead.

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