login

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

With no annotations, the description fully discloses behavior: blocks up to 30s, returns 'still waiting' if not yet consented, callback server persists for 15 minutes across calls, and saves key to a config file. This gives the agent actionable expectations about timeouts and retry semantics.

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 well-structured with three logical sections: purpose/action, when to call, and behavioral notes. Each sentence adds necessary information without fluff. The bulleted usage guidelines improve scannability.

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?

The description covers what the tool does, when to call, and key edge cases (blocking, 'still waiting', server lifetime). However, since there is no output schema, it would be helpful to specify what a successful response looks like, not just the pending case. This is a minor gap that keeps it from a perfect score.

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 tool takes zero parameters, so the schema already fully covers parameter semantics (100% coverage). Baseline for 0 params is 4, and the description doesn't need to add parameter info. It appropriately omits any parameter discussion.

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's purpose: 'Sign the MCP server in to ThumbAPI' with a specific verb and resource. It also provides concrete details about the process (opens browser, asks consent, saves API key), which distinguishes it from siblings like logout and generate_thumbnail.

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?

Explicit 'Call this tool when' section lists two clear triggering conditions: user requests authentication, or generate_thumbnail returns 'no API key found'. This provides unambiguous guidance on when to use the tool and implicitly contrasts with logout for the opposite action.

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