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

Annotations already declare readOnly/openWorld/idempotent=false/destructive=false, so safety is covered. The description adds real value by stating no Instagram login or API key is required and by listing the normalized output fields, though it omits rate limits or failure behavior.

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?

Front-loaded with the resource and modes, then parameters, then return shape, with no filler. A few clauses duplicate the schema's mode descriptions, costing it the top mark.

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 the normalized post fields (caption, likes, comments_count, views, media_url, etc.) and covers modes, parameters, and the auth model. An agent has everything needed to invoke it 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 description coverage is 100% and the schema already documents mode, limit, and query thoroughly. The description's restatement of mode semantics and the 1-20 limit is largely redundant with the schema, so it lands at the baseline.

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+resource (fetching Instagram posts as JSON) and enumerates the four modes it supports. An agent can tell this retrieves posts rather than comments, but the description never explicitly contrasts itself with siblings like instagram-comments or tiktok.

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 clearly maps each mode to a use case: profile for an account's posts, hashtag for a tag, search/user for keyword-driven discovery. That is strong conditional guidance, though it stops short of naming exclusions or rival tools to prefer instead.

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