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

readOnlyHint=true already tells the agent this is a safe read, so the description's added value is limited to naming included relations and the endpoint shape. It does not clarify that the relation set is controllable/pay-per-relation (that lives in the schema) or what happens if a relation is not requested, which risks the agent assuming Contact/type/notes are always present.

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, front-loaded sentences with no filler; the payload summary comes before the endpoint. The raw 'GET /Account/{accountID}/Customer/{customerID}.json' adds a path template with an accountID the caller never supplies, which is mild noise for an agent.

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 simple two-parameter read with no output schema, annotations covering read-only and a fully documented schema, the description supplies the essential shape of the response. The only shortfall is not tying the returned relations to the optional relations parameter.

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 relations parameter is fully documented in-schema down to the rate-limit cost and defaults, so the description need not repeat it. Mentioning Contact, customer type and notes echoes the default relation set but adds no new meaning for customer_id beyond its pattern/description.

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 ('One customer by customerID') and enumerates the key returned data (Contact, customer type, notes), which cleanly separates it from lightspeedrseries_list_customers. It stops short of naming that sibling explicitly, so differentiation is implied rather than stated.

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?

Usage is only implied: the 'by customerID' phrasing and the schema hint that the ID comes from lightspeedrseries_list_customers together tell an agent this is the single-record fetch. There is no explicit when-to-use versus list_customers, nor any note on error behavior for a missing ID.

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