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

Annotations already declare readOnlyHint=true, so safety is covered; the description then adds real behavioral context beyond the annotations: matching is exact-only, non-unique fields such as name may return multiple results, and output lands in a `customers` object. It omits things like empty-result behavior, result caps, and pagination, keeping it short of 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?

A single dense sentence front-loads the lookup keys and multiplicity caveat, then the result location. The trailing 'Checkfront: GET /api/3.0/customer' is vendor/endpoint traceability that adds little for an agent deciding how to call the tool, so it is not perfectly waste-free.

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 compensates by naming the `customers` result object, and it covers the multi-result risk from ambiguous keys — the two things an agent most needs here. All four parameters are additionally documented in the schema, so nothing essential is missing for correct invocation.

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 each parameter is already documented as an exact match in the schema, so the description's 'exact matches' framing largely restates structured data. Baseline 3 applies; the multiplicity note for name adds a little value but no format or syntax guidance beyond the 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 ('Look up customers') plus the exact lookup keys (email, full name, phone), so the agent knows precisely what the tool retrieves. It does not name the sibling checkfront_get_customer or any other alternative, so it stops short of full sibling differentiation.

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?

The description implies the usage context by naming the searchable fields and noting that non-unique fields can return several matches, which hints at when a search (vs. a single-record get) is appropriate. However, it gives no explicit when-to-use/when-not-to-use guidance and never routes the agent to checkfront_get_customer for id-based retrieval.

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