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

Annotations already declare readOnlyHint=true, so the safety profile is covered. The description adds meaningful context by enumerating what the response contains (addresses, currency, payment terms, credit limit) and naming the underlying endpoint, which helps an agent know what it gets back.

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 efficient sentence that front-loads the operation and lookup key, followed by the field list and endpoint. No filler 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 usefully summarizes the returned fields, and the single input param is fully specified. It is nearly complete; only the not-found/error behavior and any field-format caveats are absent.

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 customerGuid parameter includes a format pattern, so the schema fully documents the input. The description only restates that lookup is by Guid, adding no syntax or format detail beyond the schema — baseline 3.

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 ('Fetch'), resource ('a single customer'), and key ('by Guid'), and enumerates the payload fields (contact details, addresses, currency, payment terms, credit limit). This clearly distinguishes it from list_customers and the create/get siblings.

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 'by Guid' scoping implies this is for retrieving one known customer, but there is no explicit when-to-use guidance or reference to the alternative list_customers for browsing/filtering. Usage is inferable but not stated.

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