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

Annotations only declare the bare safety profile (write, non-idempotent, non-destructive, closed-world). The description adds genuinely valuable behavior an agent could not infer: what gets pushed to the inbox, that webhook pushes are optional, and critically that the api_key is shown only once and must be stored.

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?

A single front-loaded sentence delivers the value proposition, followed by a short imperative warning about the api_key. The first sentence is run-on, but every clause carries information an agent needs, and nothing is redundant.

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 9-parameter mutation tool with no output schema and low schema coverage, the description covers outcomes and the critical key-storage caveat well. However, it omits the semantics of most input fields and does not mention what happens on duplicate registration, which matters given idempotentHint=false.

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 only 22% across 9 parameters, so the description must compensate. It explains webhook_url, list_in_directory, and accept_messages implicitly ('so other agents can message you'), but says nothing about name, description, skills, contact, url, or agent_card_url, leaving the six remaining params undocumented in both places.

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 your agent') and enumerates the concrete outputs: api_key, inbox, signed webhook pushes, and an optional directory listing. This is unmistakably distinct from every sibling (list_agents, get_inbox, send_message), so an agent can identify it without opening the schema.

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 benefit list implies when to call it (you want an api_key or inbox) and the title marks it optional, but there is no explicit when-not guidance, no mention of re-registration behavior, and no named alternative for agents that only want to read data.

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