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

Goes beyond the readOnlyHint annotation to disclose the URL's validity window (30 min), that no token is required, that the response includes a ready curl command, and size/duration limits (25 MB / 120 s). Missing only what happens on expiry or failure modes, but the key operational traits are covered.

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 sentences, front-loaded with the eligibility envelope and benefit, then operational instructions. Slightly dense but every clause (limits, URL validity, parallel guidance, assign_to) earns its place. 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 2-param read-only tool with no output schema, the description covers purpose, constraints, response shape (URL + curl), and usage pattern. It omits URL expiry behavior and any auth context, but the annotations already declare readOnly/no-destruction.

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 100%, so parameter names are documented. The description adds value beyond the schema by explaining the assign_to effect ('put it on a screen at once') and implying how project_id scopes the URL. This is more than the baseline.

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 ('returns a signed upload URL') and enumerates exactly which file types are eligible (screenshots, MP4/WebM screen recordings, music). It distinguishes itself from upload_media by making clear this is for disk-based files and from base64 paths.

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?

Explicit when-to-use ('files on your disk'), a direct comparison ('much faster than base64'), and operational guidance ('run one command per file — in parallel'). The '?assign_to=<device id>' hint tells the agent exactly how to route the upload.

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