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

Annotations already declare readOnlyHint, openWorldHint and destructiveHint=false, so the safety profile is covered. The description goes beyond them by disclosing the exact returned fields (engagement metrics, ai_label with detection_method) and, importantly, the billing cost of $0.006 per page — cost information an agent cannot get from annotations.

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 tight sentences, front-loaded with the core purpose, then the sibling alternative, then return fields and cost. No filler or redundancy.

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 carries the return-shape burden and does so by enumerating fields and the AI label. Cost is disclosed. The only remaining gap is output volume/pagination behavior across up to 20 pages, which an agent might want when estimating a query.

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 pages, query and get_sentiment are already fully documented, including query constraints (# and @ disallowed) and the sentiment surcharge. The description adds return-value detail but no additional parameter semantics, so the baseline 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?

States a specific verb and resource ('Search Instagram posts by keyword') and explicitly distinguishes itself from the nearest sibling by naming instagram_hashtag_posts for hashtag feeds. An agent can identify the resource and its scope 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?

Provides clear routing guidance: use instagram_hashtag_posts for a hashtag's feed, implying this tool is for keyword search. It does not, however, address the nearby search_instagram_users sibling or when keyword-only search is inappropriate, so it stops short of full when/when-not coverage.

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