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

Annotations already cover readOnly/non-destructive/openWorld, so the description adds value by disclosing the negative guarantee that the payer's management link and checkout token are never returned — a real privacy behavior. It stops short of describing error/not-found behavior, keeping it from a 5.

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 resource and id, followed by return contents, the privacy exclusion, and the endpoint. It's dense but every clause earns its place; the long parenthetical field list is the only slight readability cost.

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 shoulders the burden of describing return contents and does so (subscription, payment method, discount, amounts, custom fields) plus what is excluded. Only failure modes (invalid/missing id) are unaddressed.

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% and the single customer_id parameter is already documented in the schema, including its source (moonclerk_list_customers). The description only restates 'by id', so 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 (get) and resource (one MoonClerk customer/plan) scoped by id, and enumerates the payload it returns, which cleanly separates it from moonclerk_list_customers. An agent can distinguish it from all siblings without opening the 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?

'By id' plus the GET /customers/{id} endpoint makes the retrieval pattern explicit, and read-only tells the agent this is a safe fetch. It doesn't explicitly state when to prefer it over moonclerk_list_customers, though the schema's id hint partially bridges that gap.

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