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

With no annotations, the description carries the full burden and does disclose meaningful mechanics: this initiates a resumable upload and returns PUT destinations rather than uploading bytes itself. It does not state permission requirements, size limits, or auth needs, but the two-phase behavior is unusually well surfaced.

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 tight sentences, front-loaded with the core action and the return value, followed by a routing rule for the out-of-scope case. Every sentence earns its place, though the closing 'give them the space's page' is slightly vague.

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 2-param mutation tool with no annotations and no output schema, the description conveys the return shape (PUT targets). But it leaves the completion path (finish_upload), auth/permission prerequisites, and resumable protocol constraints unaddressed, which the agent likely needs.

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 only 50% (space_id documented; file name/size only partially). The description adds useful meaning about which files qualify (photos/video the person shared), but says nothing about the required name/size fields or the array structure beyond what the schema provides.

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 ('Starts resumable uploads for capture files') and even implies the initiation role versus a completion step via 'Starts... returns where to PUT'. It does not name the sibling finish_upload, so the distinction from that adjacent tool is left to inference.

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 a clear when-to-use condition ('capture files you hold... the person shared with you') and an explicit when-not with an alternative path for files on the person's own device. However, it omits the natural next step in this API (finish_upload) that the agent needs to complete the flow.

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