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

Annotations already declare the write/non-destructive/non-openWorld profile, so the bar is lower. The description contributes the auth context (acts under the signed-in partner) and the 'password must meet portal rules' validation constraint, but says nothing about duplicate-email behavior, side effects, or what is returned.

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?

Two short sentences, front-loaded with the action and scope. The second sentence partially restates schema requirements, though the 'portal rules' constraint earns its place.

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?

All five parameters are documented in the schema and annotations cover the safety profile, but for a create/mutation tool the description leaves open duplicate handling, permission requirements, and success behavior — all things only prose could supply since there is no output schema.

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 the baseline is 3. The description adds one hint not in the schema — that the password is validated against portal rules rather than being any string — but says nothing about optional fields like intentId or country.

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 ('Create a merchant') and adds the scoping constraint 'under the signed-in partner'. It doesn't reconcile the naming mismatch between 'Customer' (tool name) and 'merchant' (description), but the action is unambiguous and no sibling tool competes for this operation.

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?

No statement of when to use this versus LookupCustomer (e.g. check for an existing merchant first) and no exclusions or preconditions beyond 'signed-in partner'. The only guidance is a restatement of which fields are required, which the schema already enforces.

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