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

Annotations already cover the safety profile (readOnly, openWorld, non-destructive), and the description adds a genuinely useful caution that results contain personal data (names, emails, addresses). It also discloses the expansion mechanism (`with`). It stops short of explaining pagination or result ordering.

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 compact sentences with the resource and PII caveat front-loaded followed by the filter/expansion details. No wasted prose, though the endpoint string is redundant for an agent.

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 16-parameter read-only list tool with no output schema, the description covers resource identity, return content, filterable dimensions and expansions. Pagination behavior is only hinted at in the schema (items_per_page note), a minor gap given annotations already signal a safe read.

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 75%, so the baseline is 3. The description groups the filterable fields (email, name, number, type, postal code, town) and lists the `with` expansion values, which adds some semantic framing, but it omits the date-range filters (created_after, updated_before, last_order_*) and full_text, leaving several params described only in the schema.

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 ('List contacts') and clarifies the entity scope with examples of contact kinds (customers, suppliers). An agent can distinguish it from the single-record plentymarkets_get_contact, though it doesn't name that sibling 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 implied by the filter list and the `with` expansion note, but there is no explicit 'use this when…' or exclusion against plentymarkets_get_contact or the other list_* tools. The agent must infer that this is the bulk/query path.

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