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

The readOnlyHint=true annotation already establishes this is a safe read. The description adds useful context by enumerating the returned field set and citing the underlying endpoint, but says nothing about auth requirements, error behavior for missing ids, or rate limits.

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 front-loaded sentence that leads with what is returned and follows with the field inventory. The trailing 'GET /contact/{id}/' is mildly redundant with the tool name but costs little.

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 carries the burden of describing return values and does so adequately via the field list. For a one-parameter read tool this is close to sufficient, though it omits failure modes and any note that the id must come from the list tool.

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 coverage is 100% and the single id parameter is fully documented in the schema, including its provenance ('from vyfakturuj_list_contacts'). The description adds no parameter-level detail 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?

The description names a specific verb and resource ('One address-book contact') and enumerates the returned field groups (billing/delivery address, ICO/DIC, e-mails, default texts, days_due), so the agent knows exactly what this fetches. It does not explicitly contrast itself with the sibling vyfakturuj_list_contacts, so it falls short of a 5.

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 implied by the singular-resource framing and the id parameter, but the description never states when to use this versus vyfakturuj_list_contacts or that the id must come from a prior listing. No exclusions or prerequisites are given.

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