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

The description adds substantive behavior beyond the annotations: it returns a job whose result is a capture id (the async job pattern tied to wait_job/get_job), it is free of credits, and it asserts a legal/rights confirmation. The annotations (openWorldHint, non-idempotent, non-destructive) cover the safety profile, but the description usefully adds the cost and legal-attestation context those annotations cannot express.

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?

Five compact sentences, each carrying distinct information (behavior, downstream use, cost, legal attestation, domain limits), with the core action front-loaded. No filler or redundancy.

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 correctly explains the return value (a job resolving to a capture id) and the async workflow. It stops short of explicitly warning that repeated calls create new captures (non-idempotent), which would matter for an agent retrying, but it is otherwise complete for a capture tool.

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 both url and viewport (including the enum and default) are already fully documented in the schema. The description contributes only the port restriction (80/443) on the URL, which is a meaningful constraint but does not go beyond baseline for the parameters themselves.

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 gives a specific verb and resource ('Opens a public web page in a sandboxed browser, records its text, pictures and layout') and names the two sibling tools that consume its output (ugcfans_make_launch_film, ugcfans_make_site_sting). An agent can distinguish this capture tool from the get_capture/get_job siblings 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?

It clearly positions the tool as the upstream step for make_launch_film and make_site_sting and states eligibility constraints (only http/https on ports 80 and 443). However, it never explicitly states when NOT to capture or how it relates to non-consumer siblings like get_capture, leaving that routing to inference.

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