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

Annotations already declare readOnlyHint and openWorldHint, so the safety profile is covered. The description adds value beyond that with the credit cost and an explicit enumeration of returned fields (likes, comments, views, caption, owner, media URLs) — important since no output schema exists.

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?

Two short sentences, front-loaded with the action and resource, then the payload and cost. Slight redundancy between the title 'Get one Instagram post or reel' and the opening sentence, but nothing wasteful.

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 the returned fields is exactly the compensation needed, and the cost note is useful. The main gap is the absence of any routing guidance relative to the many instagram_* siblings, but for a simple read tool this is close to complete.

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 itself explains that url and shortcode are alternatives ('Pass this or shortcode'). The description adds nothing about parameter form or the either/or relationship, so 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?

States a specific verb (Get) and resource (one Instagram post or reel), and the singular scope is implied against the plural instagram_posts sibling. It does not explicitly name that sibling or contrast with instagram_media, so the differentiation is only implicit.

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 when-to-use or when-not-to-use guidance. An agent must infer that this is for a single post versus instagram_posts, instagram_media, or instagram_reels, and the description never states that inference or any preconditions.

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