check_username

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

Annotations already declare read-only, open-world, and idempotent hints. The description adds substantial behavioral context: it checks three specific platforms, reveals online history and account age, and interprets an absent result as a sock-puppet signal. It also notes 'no key' meaning no API key required. No contradiction with annotations.

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?

The description is concise (two short paragraphs), front-loaded with the core functionality, and every sentence adds value. No redundant or vague language.

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?

Given the tool's simplicity, the presence of an output schema, and thorough annotations, the description is complete. It explains the platforms, the unique signal (sock-puppet), and the use case. The output schema would cover return format details, so no further description needed.

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?

The input schema already provides descriptions for both parameters ('username' and 'response_format'). The description adds minimal parameter semantics beyond noting that no key is needed. Schema coverage is effectively high despite stated 0% in context signals (likely an error), so baseline 3 applies. The description does not elaborate on parameter formats or constraints.

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 clearly states the tool checks usernames across GitHub, Reddit, and Keybase, reveals online history and account age, and signals sock-puppet accounts. It uses a specific verb ('check') and resource ('username'), and distinguishes from sibling tools by listing specific platforms and the unique sock-puppet insight.

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?

The description provides explicit usage context: 'Use when: you have a recruiter's handle/username to vet.' It also suggests a complementary action ('web-search the username' for broader coverage), but does not explicitly state when not to use this tool, leaving room for minor improvement.

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