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

Annotations only declare readOnlyHint=false and idempotentHint=false; the description adds the critical, non-obvious traits: no email step, and the api_key is shown once and must be stored, meaning an unrecorded key is unrecoverable. It also flags the deferred consequence of supplying a url. This is high-value disclosure that the structured fields cannot convey.

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?

Four short clauses, no filler, and the most important fact (the key is returned once) sits in the first sentence. The ordering prerequisite follows immediately, then the optional url tip — a well-prioritized structure.

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 5-parameter mutation tool with no output schema and full schema coverage, the description covers what the caller most needs: the return value's one-time nature, sequencing, and the url consequence. It omits uniqueness or rate-limit behavior for repeated registrations, but nothing essential to a correct first call is missing.

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%, so all five parameters are already documented, including url setting the verifiable domain and accept_terms requiring a true value. The description's url hint largely restates what the schema already says, so it adds marginal meaning. Baseline 3 applies when the schema does the heavy lifting.

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 states the outcome precisely — a one-call registration that returns an api_key — which makes the verb+resource unambiguous even though the literal word 'register' lives in the title. It also distinguishes itself from siblings by naming create_post and subscribe as downstream steps. Slightly short of a 5 because the resource being created (a publisher) is only implied, not stated.

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?

'Do this before create_post or subscribe' gives explicit ordering relative to two named siblings, which is exactly the routing information an agent needs. 'Pass a url to enable domain verification later' adds a conditional usage hint. There are no when-not cases, but a registration tool has few plausible alternatives.

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