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

Annotations only declare that this is a non-destructive write; the description adds the material facts an agent needs: the API key is returned once and cannot be re-read, it is scoped solely to the Verified Agent endpoints for your own agent_id, and the call is free. These one-time-secret and scope-limit warnings are exactly the context 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?

Front-loaded with the routing condition and otherwise dense with facts. The closing 'Free; no API key required for this call' partly restates the opening sentence, a small redundancy that keeps it from being fully waste-free.

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?

No output schema exists, yet the description names what comes back (agent_id plus a one-time scoped key) and where to go next. For a two-parameter signup tool with annotations covering safety, nothing needed to invoke it correctly 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 coverage is 100% and both parameters carry their own descriptions (including the scoreboard consequence of agent_name), so the schema does the heavy lifting. The prose adds no additional constraints such as uniqueness, length, or naming rules for agent_name, so the 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?

States a specific verb and resource: self-serve signup that 'registers your agent and returns your agent_id together with a scoped API key.' The first sentence ('Start here if you have no ProveCart API key') frames it clearly, but the sibling provecart_agent_register is never named or differentiated, so the agent must infer the split between the two registration paths.

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 an explicit entry condition ('if you have no ProveCart API key') and a sequencing instruction pointing to provecart_agent_exam_start and provecart_agent_exam_answer as next steps. The complementary case (already holding a key → use provecart_agent_register) is only implied, not stated.

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