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

Annotations already establish readOnlyHint and openWorldHint, so safety is covered. The description adds genuinely useful behavior beyond that: fixed page size (12), newest-first ordering, cursor-based paging, the specific fields returned, and a cost of 1 credit. These are non-obvious traits an agent should know before calling.

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, front-loaded sentences covering purpose, page shape, paging mechanics, and cost with zero filler. Every sentence earns its place.

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 usefully enumerates return fields and page size, and annotations cover the safety profile. The one gap is that it never states the request must be scoped to a user (via user_id/username), which matters for a multi-sibling family.

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 cursor, user_id, and username are all documented in the schema itself. The description's mention of paging with cursor adds nothing beyond what the schema already says, 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?

Clear verb+resource: it retrieves a list of recent Instagram posts and specifies the shape of the result (likes, comments, views, caption, media URLs). However it never says whose posts (a specific user's timeline) nor distinguishes itself from close siblings like instagram_post, instagram_tagged, or instagram_media, leaving the agent to infer scope.

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?

The description gives no when-to-use guidance and names no alternatives, despite an unusually dense sibling set (instagram_post, instagram_tagged, instagram_media, instagram_reels). It also never states that a user_id or username is needed to scope the request, which the schema implies but the prose omits.

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