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

Annotations already declare readOnlyHint=true and openWorldHint=true, so the safety profile is covered. The description adds a useful cost disclosure ('Cost: 1 credit'), which is real context beyond the annotations, but nothing about rate limits, latency, or result shape.

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 plus a cost line, fully front-loaded with the core purpose first. No padding or redundancy.

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 simple read-only lookup with annotations covering safety, 100% schema coverage, and no output schema, the description supplies everything needed to call it: purpose, relatedness semantics, and cost. Only minor gaps remain, such as expected result volume.

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%, so both user_id and username are fully documented in the schema, including the 'pass this or user_id' mutual-exclusion hint. The description adds no parameter meaning beyond the schema, 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 and resource ('Find similar Instagram accounts') and adds a clarifying gloss: accounts Instagram considers related to this one. An agent can tell it apart from instagram_search or instagram_top_accounts, though siblings aren't named explicitly.

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?

No when-to-use or when-not-to-use guidance. It never says whether this requires an existing account context or how it differs from other discovery tools like instagram_search or instagram_top_accounts, leaving selection to inference.

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