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

Annotations already declare readOnlyHint=true and openWorldHint=true, so the safety profile is covered. The description adds non-obvious behavioral context — the data comes from 'credential-free public JSON' and 'An empty `markets` list is a valid response when the category has no markets' — which prevents the agent from misreading an empty result as an error.

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-loads the core purpose, then supplies parameter sourcing, an edge-case note, and an alternative-tool pointer, with little waste. The sentences are dense but each carries actionable information, so no meaningful trimming is obvious.

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 an output schema present, return fields need not be described. The description still covers purpose, both parameters' provenance, and the empty-result edge case, leaving nothing an agent needs to call it correctly unstated.

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% (both params documented as numeric DraftKings ids), which sets a baseline of 3. The description goes beyond it by explaining what each id selects and where to find it, plus concrete example categories for `subcategory_id` (game lines, player-prop, alternate-line).

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 precise verb ('Returns') and resource ('one event's betting markets and selections for a specific market category'), narrowed to a scoped unit of data. It also names the sibling draftkings_odds, so an agent can distinguish it from related odds endpoints without inspecting schemas.

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 clear context for how to obtain both inputs (from the `id`/`subcategory_id` fields of a DraftKings odds response or event-page network traffic) and routes to the alternative tool: 'Use draftkings_odds to retrieve DraftKings Sportsbook odds.' No explicit 'when-not-to-use' exclusion is stated, keeping it just short of 5.

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