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

Annotations already declare readOnlyHint=true and openWorldHint=true, so the safe-read profile and external-dependency nature are covered. The description adds no behavioral context beyond routing — no pagination behavior, result limits, or auth/rate-limit notes (pagination is only hinted at via the schema's page_token). Adequate but adds little beyond structured data.

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?

A single tight sentence with the purpose front-loaded and the routing condition appended. No filler, no repetition of schema or annotations.

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 read-only listing tool with an output schema, complete parameter docs, and safety annotations, the description supplies the one thing structured data cannot: the sibling-routing decision. Return format is legitimately omitted since an output schema exists; only minor gaps (result volume/pagination expectations) remain.

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% with rich per-parameter text (ID pattern and source, page_token reuse warning, content_type enum), so the schema carries parameter meaning. The description only restates the ID-vs-URL routing condition already present in the user_id schema field, adding no new parameter detail. Baseline 3.

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 — reading a Toutiao user's published works ('读取头条用户发布的作品') — and immediately distinguishes this tool from the profile-URL variant. An agent can tell which of the two sibling post-listing tools to pick from the description alone.

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 explicit routing conditions: use this when a numeric user ID is already available, use the profile-link tool when a homepage URL is available. The when/when-not split with an alternative is fully specified, not inferred.

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