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

Annotations already declare readOnly/idempotent/non-destructive/openWorld, and the description adds genuinely new behavior: reverse-chronological ordering, the shape of returned items, and a pricing model (¥0.3 per call, billed only on success, auto-refund on failure or empty results). That billing detail is the kind of operational context annotations cannot express; it lacks only notes on rate limits or pagination.

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 short clauses ordered purpose → return shape → usage → billing, with no filler. Each sentence carries distinct information, though the billing note could be compressed slightly.

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 describing the return content (ordered list, item IDs, basic engagement metrics). Combined with the billing note and the small two-parameter schema, an agent has enough to invoke it correctly, though pagination or result-count limits are unaddressed.

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 are already documented in the schema. The description implies the username identifies the target account but adds no format, case-sensitivity, or handle-vs-URL guidance beyond what the schema provides, which matches the baseline of 3 when the schema carries the burden.

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 states a specific verb and resource ('获取Instagram用户帖子列表') and scopes the result ('按时间倒序，含每条内容ID与基础互动数据'), so an agent can distinguish it from profile-level tools like ig_user_info. It stops short of naming a sibling to contrast with, so it is clear but not maximally differentiating.

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 gives three concrete use cases (monitoring posting frequency, content strategy, bulk-fetching content IDs), which is a clear positive signal for when to pick this tool. It does not state when NOT to use it or name an alternative such as ig_keyword_search or ig_post_detail.

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