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

Annotations cover the safety profile (readOnlyHint, openWorldHint), and the description adds genuinely new context beyond them: the 1-credit cost and the public-account restriction. It stops short of explaining failure behavior for private or nonexistent accounts.

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: purpose and returned fields first, cost last. Zero filler, everything front-loaded.

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 compensates by listing returned fields, and the cost/access constraints round it out. Minor gaps remain around error or private-account behavior, but an agent has what it needs to call this 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 description coverage is 100% — both user_id and username are fully documented, including the '@'-optional handle and URL acceptance. The description adds no parameter-level meaning, so the 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+resource ('Get an Instagram profile') and enumerates exactly what comes back (counts, bio, links, category, verification, HD picture). It does not explicitly differentiate itself from nearby siblings like instagram_username, instagram_user_id, or instagram_check, so it falls 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 only implied: 'any public account' hints at the public-only constraint, but no when-to-use or when-not-to-use guidance is given, and no alternative (e.g. instagram_username or instagram_check) is named for overlapping needs.

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