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

Annotations already declare readOnlyHint=true, so the safe read nature is covered. The description adds the upstream endpoint mapping and a preview of returned fields, but says nothing about auth requirements, error behavior for a missing/invalid Guid, or rate limits. Modest added value on top of annotations.

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?

One sentence, front-loaded with the action and identifier, followed by the field inventory and endpoint. No padding or redundancy.

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 partially compensates by listing the main fields returned, and annotations cover the read-only safety profile. Missing only error/not-found behavior, which is minor for a single-Guid lookup.

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 parameter carries its own description plus a Guid regex pattern, so the schema does the heavy lifting. The description's 'by Guid' adds only a light restatement, matching the baseline for fully documented schemas.

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 ('Fetch a single customer by Guid') and enumerates the returned field groups (contact details, addresses, currency, payment terms, credit limit). The 'single ... by Guid' phrasing implicitly separates it from unleashed_list_customers, but no sibling is named explicitly.

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: 'by Guid' signals you need a known identifier rather than search criteria, which nudges the agent toward this tool over unleashed_list_customers. There is no explicit statement of when to prefer this over the list endpoint or what to do when the Guid is unknown.

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