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

Annotations already cover the safety profile (readOnly, idempotent, non-destructive, non-open-world), and the description goes further by disclosing billing per returned row, that limit caps both rows and cost, that returned rows are collection metadata rather than story items, and that the content is untrusted user-generated input. These are behavioral traits no annotation conveys.

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 compact sentences, front-loaded with purpose then routing then output then cost/safety caveats. Every sentence carries distinct information; nothing is redundant padding.

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 enumerating the returned fields (pk, id, title, media_count, is_pinned_highlight, created_at, user_pk) and clarifying they are collection metadata. Together with the cost and trust caveats, an agent has everything needed to call and interpret the tool correctly.

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 coverage is 100%, so the baseline is 3, but the description adds semantics the schema does not: limit is not merely a row cap but a cost cap (billed per returned row). It also clarifies what the returned rows represent. This meaningfully exceeds the schema's plain '1-100' range statement.

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 ('Get an Instagram user's story highlights') plus ordering ('newest first'), and explicitly differentiates from two siblings: get_highlight_by_id for a single highlight and get_user_stories for individual stories. An agent can distinguish this tool from its neighbors without opening any 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?

Names the two plausible alternatives by name and gives the condition that selects each (list collections vs. one highlight vs. individual stories). This is explicit when-to-use and when-to-use-something-else routing.

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