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

Annotations already declare readOnlyHint=true, idempotentHint=true, destructiveHint=false and openWorldHint=false, so the safety profile is covered. The description adds the error contract (not_found for unknown/non-public ids) and implicitly scopes the response to 'public' fields. Its field enumeration is largely repeated by the output schema, so it adds less behavioral content than it appears.

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?

Front-loaded with purpose, then usage, then error behavior — good ordering with no filler. The long list of returned fields is the one soft spot, since an output schema already exists and makes much of that enumeration redundant.

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 single-param read tool with full annotations and an output schema, the description covers everything an agent needs: what it returns, when to prefer it, id provenance, and the not-found path. Nothing material is missing.

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 0%, so the description must carry the parameter. It does: the id is a UUID, and critically it specifies where the value comes from ('the id field of search_events or recently_updated_events'). No guidance on malformed-UUID handling, but the format is documented 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+resource+scope: 'Get the full public details of one German flea market by its UUID.' It also anchors the id to the sibling tools that produce it (search_events, recently_updated_events), so an agent can distinguish this detail-fetch from the discovery tools without opening a schema.

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?

Gives an explicit trigger: 'Use it when a search hit is not enough to answer about price, address or what is sold,' which implicitly routes discovery to the sibling search tools. The failure condition ('Unknown or non-public UUIDs return not_found') is also disclosed.

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