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

Annotations only declare the mutation profile (readOnly=false, idempotent=false, destructive=false); the description adds substantial non-obvious behavior — the one-time API key return, that repeats never return it again, that the key authorizes REST while hosted MCP tools still need OAuth, and that the key must be kept private.

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?

Front-loaded with the core action, followed by the security and lifecycle caveats. Sentences are dense but each carries a distinct fact (key secrecy, REST vs OAuth scope, non-repeatability, existing-account exclusion), with only slight redundancy around the code-handling warning.

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 two-parameter mutation tool with no output schema, the description covers what is created, the one-time credential behavior, and channel restrictions. It does not address failure modes (invalid/expired code) or the resulting account state after creation, leaving minor gaps.

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%: 'code' is documented as a six-digit email code and 'signup_token' as the token from revdoku_signup. The description reinforces where the code comes from but adds no syntax or format detail beyond the schema, 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?

States a specific verb and resource: verify the emailed code and create the account, first mailbox, and scoped API key. This is clearly distinguishable from revdoku_signup, revdoku_signup_resend, and revdoku_status, which handle the surrounding flow rather than the verification step.

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?

Gives real routing guidance: 'Existing accounts require normal sign-in' tells the agent when not to call this, and 'Use a private application input for codes, not ordinary chat' specifies how to collect the code. It stops short of explicitly naming revdoku_signup or revdoku_signup_resend as the prerequisite/alternative tools.

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