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

Annotations already declare readOnlyHint=true and destructiveHint=false, so the safety profile is covered. The description still adds real behavioral context beyond them: it reads live from Instagram, is slower than the other tools, and covers one account at a time.

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 sentences, front-loaded with what it returns, then when to use it, then the operational caveat. Given there is no output schema, enumerating the returned fields earns its space rather than wasting it.

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 carries the burden of describing return fields, and it also discloses latency and per-account scope. Nothing material is missing for an agent to call 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 coverage is 100%, so limit and instagramAccountId are already documented with ranges and sourcing. The description adds the 'newest first' ordering and the single-account scope, though the schema's own parameter text largely duplicates these points.

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 names the resource (posts and reels on a connected Instagram account), the shape of the result (caption, media type, publish time, link, likes, comments) and the ordering (newest first). An agent can immediately tell this is the read-only listing tool and distinguish it from the per-post stats sibling.

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 gives three concrete triggering scenarios ('what have I posted lately', finding the best performer before campaign placement, and fetching the post id that campaigns_create needs). It stops short of stating when NOT to use it, e.g. reaching for instagram_post_stats when per-post detail is wanted.

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