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

Annotations already declare readOnlyHint=true and openWorldHint=true, so the safety and open-web profile is covered. The description adds genuinely new context — the returned fields (id, title, cover) and the '(1 credit)' cost per call — which the annotations do not provide. It still says nothing about volume of results, ordering, or behavior when the profile is private.

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?

A single compact sentence that front-loads the resource and then the output fields and cost. It earns most of its words, though the parenthetical credit note and field list would read better as separate clauses.

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, listing id/title/cover is a useful partial substitute, and the credit cost is disclosed. However, for a tool in a crowded Instagram family with a near-twin sibling, the absence of any routing or scope note leaves a real gap.

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%: handle and user_id are both documented, including the 'Send this or handle' alternative, so the schema does the heavy lifting. The description adds no further parameter meaning beyond implying that a profile identifier is needed.

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?

Names the resource (a profile's story highlights) and lists the returned fields (id, title, cover), but gives no verb such as list/return and never distinguishes itself from the closely named sibling instagram_highlight_detail. An agent must infer that this is a collection-returning read and that the sibling fetches a single highlight.

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?

There is no guidance on when to call this versus instagram_highlight_detail or instagram_profile, no prerequisites, and no statement about whether one of handle/user_id is required despite both being marked optional. The only hint is implicit in the word 'profile's'.

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