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

Annotations already declare readOnlyHint=false and idempotentHint=false, so 'WRITE' and 'Not idempotent' mostly restate structured data. However, the description adds genuinely new operational context: the required OAuth scope (write_customers) and the concrete endpoint (POST /api/3.0/customers.json), which an agent needs for auth planning and debugging.

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?

Five short fragments, each carrying distinct information, with the most decision-relevant fact ('WRITE') front-loaded. No filler, no repetition of the title.

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 mutation with no output schema and no annotations beyond safety hints, the description covers the action, the precondition, the non-idempotency, the permission, and the endpoint. It stops short of telling the agent what a successful response contains (e.g. the new customer id) or how duplicate email/phone per store is handled, which matters given the schema's 'unique per store' note.

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%, so the baseline would be 3, but the description adds meaning the schema lacks: the schema lists zero required parameters, and only the description reveals that at least one identity field (first_name/last_name/email/phone) must be supplied. That is a real constraint not encoded anywhere in the input schema.

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 customer') and disambiguates from the many read/list siblings by leading with 'WRITE.' An agent can immediately tell this apart from easystore_list_customers, easystore_search_customers, and easystore_get_customer.

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?

'Pass at least one of first_name, last_name, email or phone' is a concrete precondition for a successful call, and 'Needs write_customers' tells the agent the required scope. It does not explicitly say when to prefer easystore_update_customer instead, but the create-vs-update distinction is self-evident from the name.

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