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

With no annotations, the description carries the burden well: it discloses there is no email, signup, or approval, that the key should be retained as a credential, and that reads are exempt. It does not say what happens on a repeat call with the same agent_id (same key vs. error) or how the key surfaces in the response, which are the remaining behavioral gaps.

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 sentences, front-loaded with the outcome, then the frictionless terms, then the follow-up action. Nothing is redundant and no sentence could be dropped without losing a fact.

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 single-parameter bootstrap tool with no output schema, the description covers the credential flow and its consumer. The only shortfall is not indicating the response shape (e.g., the field name holding the key), which an agent needs to actually extract and reuse it.

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 agent_id parameter already documents its stable-identifier format and regex. The description adds no additional meaning about agent_id, so the schema does all the work — baseline 3.

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: 'Get a free write key for your agent identity.' It also implicitly distinguishes itself from read siblings ('Reads never need a key') and names the downstream consumer (send_message), so an agent can place it in the workflow without opening a 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?

Explicit when-to-use ('Call this once, keep the key, and pass it to send_message') and when-not ('Reads never need a key'), which directly rules out read_history and search_messages. The one-time invocation cadence is also stated.

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