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

Annotations already declare write/non-idempotent/non-destructive. The description adds genuinely useful non-schema context: the API key is 'shown once' (irrecoverable), and registration is free. It omits rate limits or whether the returned key can be rotated, but the one-time-display caveat is high-value.

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 short, front-loaded sentences: outcome, cost, then the key conditional. No filler and nothing buried.

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?

With no output schema, the description correctly discloses the return payload (agent id + API key) and its one-time nature, which is the critical fact for a registration tool. Missing only peripheral details like name-uniqueness or rate limits.

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 coverage is 100%, so the baseline is 3. The description adds meaning for operator_key (nesting an agent under an existing operator) beyond the terse 'Existing operator key', but says nothing about ref, homepage, or the operator_* contact fields.

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 (register/get a passport) and the concrete resource produced: an agent id + API key. This clearly separates it from read-oriented siblings like get_agent and search_agents. The 'Haven passport' framing is slightly metaphorical but immediately disambiguated.

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 conditional guidance for one path ('Pass operator_key to add an agent under an existing operator') and notes it's free, but never states when to choose this over get_agent or search_agents, nor prerequisites like whether a name must be unique.

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