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

readOnlyHint=true already tells the agent this is a non-mutating read, so the description needn't restate safety. It adds the REST endpoint mapping, which is mildly useful context, but nothing about failure modes (e.g. 404 on unknown id) or the shape of the returned contact. Adequate but thin for the burden placed on it.

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 sentences, zero filler, with the core action ('Fetch a single contact') front-loaded before the endpoint decoration. Nothing could be trimmed without losing information.

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 tool with full schema coverage and a safety annotation, the essentials are present. The only gap is the absence of any hint about error handling or whether the embed parameter affects response size, which is minor here.

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% – contact_id and embed are both documented in the schema, including the comma-separated expansion syntax. The description adds no parameter-level meaning beyond that, so the baseline 3 applies.

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) and resource (a single contact) with the scoping word 'single', which implicitly distinguishes it from sevdesk_list_contacts. The endpoint mapping (GET /Contact/{contactId}) reinforces exactly one record, 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: 'single contact by id' suggests retrieval of one known record versus the list tool. There is no explicit statement of when to prefer this over sevdesk_list_contacts or sevdesk_update_contact, and no mention of error behavior for a bad id.

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