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

Annotations already declare readOnlyHint=true, idempotentHint=true, destructiveHint=false and openWorldHint=true, so safety is covered. The description adds genuinely new operational context: pricing at ¥0.3 per call, billing only on success, and automatic refund on failure or empty result — material for an agent deciding whether to retry. It omits auth requirements, which the schema carries instead.

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?

Four tight sentences, each earning its place: capability, return fields, use cases, billing. The capability and return fields are front-loaded, and nothing is repeated from the 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?

With no output schema, the description correctly compensates by listing returned fields, and it covers cost/refund behavior for a paid, open-world call. The only real gap is error/edge behavior beyond refunds — e.g. what happens for a nonexistent or private account — but that is minor for a simple one-param lookup.

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 parameters (username, _token) are already documented, and the description adds no syntax, format, or resolution rules for username (e.g. handle vs. URL vs. numeric ID). Baseline 3 applies when the schema does the heavy lifting.

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 ('获取Instagram用户信息') and enumerates exactly what comes back (nickname, follower count, like count, bio, verification status). This cleanly separates it from siblings like ig_user_posts (posts) and ig_keyword_search (search), so an agent can pick it without opening the 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?

Gives three concrete use cases — influencer screening, account profiling, follower-tier grouping — which tells the agent when this tool is the right pick. It stops short of naming an alternative sibling or stating when NOT to use it (e.g. use ig_user_posts for content analysis), so it is clear context without exclusions.

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