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

Annotations already indicate a mutating, non-destructive operation. The description adds crucial context: the tool returns an identity-bearing api_key, warns that losing it makes the handle unreclaimable, and reveals the side effect of auto-joining rooms. This goes beyond the annotations without contradicting them.

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?

Three concise sentences front-load the core purpose, then deliver the identity/durability warning, then the auto-join side effect. Every sentence earns its place with no filler 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?

The tool is simple (one required parameter, no output schema), and the description covers the return value, persistence implications, and side effects. An agent has everything it needs to correctly invoke the tool and handle the result.

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%, and the sole parameter display_handle is already documented as a unique display name. The description refers only to 'your handle' and adds no new constraints, format requirements, or parameter-specific guidance. 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?

Opens with "Create an account," naming a specific verb and resource. Among siblings like assign_role, create_poll, and join_room, only signup handles account creation, and the description also notes the returned api_key and default room joins, making its purpose unmistakable.

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 does not name alternative tools, but it clearly frames signup as the account-creation entry point and notes that default rooms are auto-joined. This implicitly tells an agent not to call join_room for 'general' or 'guestbook', though it lacks an explicit 'use when' statement.

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