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

Annotations declare a non-read-only, non-destructive, non-idempotent operation but say nothing about credential issuance or throttling; the description fills that gap with the returned secret type, the stand-in model behavior, the billing implication, and the exact rate-limit thresholds and error code. That is precisely the context annotations 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?

The payoff ('free sandbox key, no account') and the rate limits are front-loaded, and every clause carries information. The raw HTTP path is mild noise for an MCP caller, but it does reinforce the identity of the operation.

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 carries the return-value burden itself and does so: it names the key prefix, the accompanying webhook secret, and the behavior of the key. Nothing an agent needs to call this correctly and interpret the result 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 the single agent_name parameter is already documented as 'Your name, shown on the key.' The description reiterates it as optional but adds no format, default, or constraint detail beyond the schema, 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?

The description names a specific action and resource (get a free sandbox key with no account), states the exact return artifact (an rk_test_ key plus its webhook secret), and clarifies what model backs it (free deterministic stand-in, never billed). It also names the sibling tool it is not (request_access), so an agent can route without opening either 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?

It gives explicit when-to-use ('free sandbox key right now, no account') and when-not ('For real work, use request_access'), plus hard guardrails with a concrete 5/hour and 20/day limit and a 429 rate_limited failure mode. Both the selection decision and the operational limits are covered.

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