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

Annotations already declare readOnly/idempotent/non-destructive, and the description adds real behavioral context: one bounded request with no background polling or retry, account-dependent access/delay/metered usage, affiliate 27 exclusion, and the warning not to infer coverage from an empty result. It does not describe the empty-result edge case mechanics in depth, but it goes well beyond the annotations.

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 the first sentence is a run-on that awkwardly splices the tool purpose into the main_line semantics, and the remainder reads as a list of disjoint policy fragments rather than a front-loaded explanation. Every clause is relevant, but the ordering and grammar cost clarity.

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?

An output schema exists so return values need no explanation, and the safety profile is covered by annotations. However, for a tool with a nested path/query object and ten-plus filtering parameters, the description omits sibling differentiation (v1 vs v2, openers/closing), ordering or narrowing advice, and the practical consequences of the market_ids cap.

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?

Reported schema coverage is 0% at the top level, though the nested query properties carry detailed descriptions of their own. The description adds some meaning by clarifying that main_line=true also excludes closed prices when selecting main lines and that canonical IDs should be reused, but it does not explain include, hide_closed, affiliate_ids, or the market_ids limit.

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 ('Get a single event with markets'), so the agent knows exactly what it returns. It does not differentiate itself from the obvious sibling v1GetEventByID or from v2GetEventOpeners/v2GetEventClosing, leaving version/scope selection to inference.

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?

No explicit when-to-use or when-not-to-use guidance, and no sibling is named as an alternative. The line 'Use returned canonical IDs' is a data-flow hint, not routing guidance, so the agent gets no help choosing this over the many other event/market endpoints.

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