Instagram post

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

Annotations already declare readOnlyHint, idempotentHint, openWorldHint and destructiveHint=false, so the safety profile is covered without prose. The description adds genuinely new behavioral information: a pricing rule ('Cost: 1 credit per successful call, failed calls are refunded'), which tells the agent retries are cheap and failures are not billed. It does not disclose behavior for private or deleted posts, which is the remaining gap.

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?

The purpose and cost are correctly front-loaded in the first two lines, which is good structure. However, the description then dumps roughly twenty return fields as one flat comma-separated block, which is hard to scan and would read better as a compact summary or omitted entirely in favor of the schema.

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 only two optional parameters and no output schema, the description carries the return-shape burden and does so by enumerating every field, including nullability. It is nearly complete; the notable omission is any explanation of the nested 'media' array for albums or what the 'type' and 'product_type' string values signify.

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%, with both parameters documented including examples and the alias precedence ('shortcode; alias used only when url is empty'). The description's restatement of 'provide one of url OR shortcode' adds nothing beyond the schema, so the baseline of 3 is appropriate.

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?

The description opens with a specific verb-and-resource pairing ('A single Instagram post/reel by URL or shortcode') and enumerates exactly what data it returns, so an agent knows this fetches one media item with its full metadata. It loses a point because it never distinguishes itself from the close siblings instagram_reel and instagram_photos, which appear to cover overlapping ground.

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 only guidance is a parameter rule ('Provide one of: `url` OR `shortcode`'), which restates the schema rather than explaining when to pick this tool. There is no statement of when-not-to-use it or which sibling to choose for a reel, a photo album, or a comment listing, all of which exist in the sibling set.

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