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

Annotations already declare readOnlyHint, idempotentHint, openWorldHint and non-destructiveness, so safety is covered. The description adds genuinely non-derivable behavior: the exact return fields (description, like/comment/share counts, account info, publish time) and the billing model (¥0.3 per call, charged only on success, refunded on failure or empty results). That cost/billing disclosure is the standout value here.

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, each earning its place: purpose plus return shape first, then usage scenarios, then pricing/billing. Nothing is redundant and the core purpose is front-loaded.

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 compensates by listing the returned fields, and it discloses cost and billing behavior — enough for an agent to decide to call it. It is slightly thin on result-set behavior (ordering, result count limits, whether keyword hits description text), which keeps it from a 5.

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 only three parameters (username, keyword, _token), so the schema already carries the parameter documentation. The description adds no semantics about how keyword matching works or what username format is expected, so the baseline of 3 applies.

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 — '在视频号账号内搜索作品' — plus the account-scoped keyword search angle that separates it from listing tools. It stops short of naming the actual sibling it differs from (channels_user_posts / channels_post_detail), so the agent must infer the boundary from the word '搜索'.

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 states concrete use cases: single-item engagement analysis, material ingestion, or as the entry point of a batch task. That's clear positive guidance, but it offers no when-not-to-use cases and does not route to an alternative tool for full-account listing or single-post retrieval.

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