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

Annotations only cover safety (readOnly, openWorld), and the description adds substantial behavioral context beyond them: URLs are signed Instagram CDN links that expire after a few hours, quality is best-available, and the call costs 1 credit. These are exactly the traits an agent cannot infer from the annotations or schema.

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 short sentences: what you get, what the URLs are, and the cost. Front-loaded with the payload description and no wasted wording; the cost line is discrete and useful for a credit-metered tool.

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 correctly explains the return value (per-slide direct file URLs in best quality) and warns about expiry. Parameters are optional and fully covered by the schema. Minor gaps remain, such as whether one call handles all slide types uniformly, but nothing essential to invoking it is missing.

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 both parameters are documented with an example URL and an explanation of the shortcode. The description adds nothing beyond that, so the baseline of 3 applies since the schema does the heavy lifting.

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: returns download URLs for a post, reel or carousel, and clarifies the payload is direct image/video file URLs for every slide. An agent can tell this is a media-fetch tool rather than a metadata tool. It does not explicitly distinguish itself from the many siblings (e.g. instagram_post, instagram_reels), so it stops short of a 5.

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?

Usage is implied rather than stated: you call this when you need downloadable files instead of metadata. There is no explicit when-to-use/when-not guidance, no mention of when to prefer this over instagram_post or instagram_reels, and no note on the url-vs-shortcode choice in the description itself.

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