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

With no annotations, the description carries the full burden and does so: it discloses no authentication is required, that the key is the ONLY credential, that it cannot be recovered if lost, and that an email can later be bound for recoverability. These are exactly the behavioral traits an agent needs before invoking.

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 primary outcome, and each sentence adds operational value (credential handling, follow-up, recovery). It is somewhat dense with em-dash clauses, but nothing is wasted or 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?

There is no output schema, so the description must explain return values, and it does (api_key, store slug + store_url, mu_credits) along with the post-call flow and credential caveats. Nothing an agent needs to call this 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?

The tool takes zero parameters, so there is nothing to document; the baseline for 0 params is 4. The description correctly indicates no input is needed and instead explains what the call returns.

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+resource and outcome: 'one call returns a guest api_key, a ready-made store (store slug + store_url) and free mu_credits'. It clearly distinguishes itself from siblings like mu_register and mu_create_store by framing itself as the instant, no-email onboarding path.

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?

Explicitly says when to use it ('the fastest way to start'), what to do immediately after ('tell the user their api_key and have them reconnect with header Authorization: Bearer <api_key>; then mu_create_product works immediately'), and names the alternative path for recovery (mu_register with the same key).

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