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

Annotations already declare readOnlyHint, idempotentHint, destructiveHint=false and openWorldHint, so 'changes nothing' largely restates them. The description does add genuinely new context — that only public data is returned and that each request costs 1 credit — but it is silent on what happens for private or nonexistent accounts and whether credits are still charged.

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, zero waste, with the core action front-loaded and constraints following. Nothing is padded or repeated for its own sake.

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?

For a single-parameter read-only lookup this covers the essentials: what it fetches, that it is safe, and its cost. The main residual gap is that with no output schema, the description does not hint at what profile fields come back.

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 single username parameter is already documented with an example covering both a bare handle and a full profile URL. The description adds no additional meaning about input format or normalization, so the baseline of 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?

The description names a specific verb and resource ('Get user profile by username'), so an agent immediately knows the operation. It does not explicitly differentiate itself from nearby siblings such as instagram_search_users or instagram_user_posts, leaving that distinction to be inferred from names.

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, and no alternative tool is named. The agent must infer that instagram_search_users should be used for discovery and this tool for a known handle, which is inferable but never stated.

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