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

Annotations already signal readOnlyHint and openWorldHint; the description adds meaningful scope behavior: it currently returns videos but not image-text posts, and supports pagination via page_token. It does not go into rate limits or failure modes, but for a read-only search tool this is adequate.

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?

The description is a single dense paragraph front-loaded with the core action and scope, followed by usage routing and parameter support. Every clause adds value; no filler or restatement.

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 filtered search tool with an output schema, the description is complete: it states the trigger condition, the alternative paths, the scope limitation, and the available controls (sort_type, duration_range, page_token pagination). Nothing needed to select and call it correctly is missing.

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%, and each parameter has a detailed description, so the tool description only needs to mention that sort_type, duration_range, and page_token are supported. It adds no syntax beyond the schema, matching the baseline for full schema coverage.

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?

Description opens with a clear verb and resource: '按搜索词搜索微信视频号视频' (search WeChat Channels videos by keyword). It also differentiates itself from siblings by noting it returns only videos, not image-text posts, and contrasts with detail/comment/speech-text tools.

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?

Explicitly states when to use ('用户需要按搜索词查找视频时使用') and when not to: if a work link or valid encrypted_object_id is already available, use detail/comment or ID-based speech-text tools directly, '均无需先调用搜索'. This gives clear routing versus the many sibling tools.

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