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

Annotations already declare readOnlyHint=true and openWorldHint=false, so the safety profile is covered. The description adds value by naming what is returned (address, contact person, VAT ID) in the absence of an output schema, but it says nothing about behavior on a missing ID or any access constraints.

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 short sentence with zero padding, and the resource and returned fields are front-loaded. It is efficient, though it is terse enough that it omits useful context rather than being optimally structured.

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 one-parameter read tool whose annotations cover the safety profile, this is close to complete, and the description compensates for the missing output schema by naming the returned fields. The only real gap is undefined behavior when the customer does not exist.

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% — the single id parameter is documented as "Kunden-ID" — so the schema does the work. The description adds no syntax, format, or lookup semantics beyond what the schema already states, making the baseline 3 appropriate.

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?

The description pairs a specific verb ("lesen") with a specific resource ("Kunden") and the singular "Einen Kunden" signals single-record retrieval, which implicitly distinguishes it from the sibling list_customers. It never names that sibling or any alternative explicitly, so the differentiation is inferable 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 singular article and the required id parameter suggest fetching one known customer. There is no explicit statement of when to use this versus list_customers, and no mention of prerequisites or error behavior for unknown IDs.

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