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

Annotations already cover the read-only, idempotent, closed-world safety profile, so the bar is lower. The description adds genuinely non-obvious operational context: an Enterprise Data key is required, supplied as an X-API-Key header on the MCP request, with a URL for obtaining it. That is exactly the kind of auth prerequisite annotations cannot express. It stops short of disclosing pagination or result-size behavior.

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?

It is short, but not front-loaded: it opens with a bare noun phrase rather than a verb and result, then packs three result shapes, a country caveat, and the auth requirement into two dense sentences. The 'without country — the list of countries' fragment spends words without conveying a determinate meaning.

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 5 optional parameters, no output schema, and a multi-shape result controlled by `kind`, the description should make the result shapes and pagination behavior unambiguous. It identifies the three shapes and the auth requirement, but leaves return structure to the schema-only `kind` descriptions and says nothing about pagination limits or result size.

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%, so the schema already documents `kind`, `page`, `buyer`, `country`, and `supplier` in detail. The description's only added semantic is a fallback/scope hint about omitting `country`, but that hint is phrased so ambiguously ('without country — the list of countries') that it is unclear whether it means a country list is returned or that results aggregate across countries. 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?

The description names the domain concept (buyer × supplier pairs where the supplier won without a rival) plus two alternate result shapes (locks, buyer shares), matching the `kind` enum. However it is written as a fragmentary noun phrase with no verb, and the trailing clause 'without country — the list of countries' is genuinely ambiguous. No sibling tool is named or contrasted, so an agent cannot tell from the description alone how assay_solo differs from assay_line or assay_contract beyond guessing from the name.

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?

There is no explicit statement of when to use this tool versus the nine siblings, and no prerequisites or exclusions beyond the auth note. The only usage-adjacent content is the cryptic 'without country' remark and an external link. The agent must infer from the tool name and the `kind` enum which of assay_* to call.

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