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

Annotations already mark the operation readOnly, idempotent, and non-destructive, and the description adds meaningful behavior beyond that: persist-then-read semantics, data sources, the no-charge available:false return on missing rows, HTTP 400 for other sports, and its nature as a price-input read rather than a trading product. This is rich, honest behavioral disclosure.

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?

The description is front-loaded with the core purpose and then delivers dense, non-redundant guidance: source providers, price format, contract scope, empty-result behavior, error behavior, and product positioning. Every sentence earns its place without fluff.

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-parameter tool with an output schema and strong annotations, the description is fully sufficient. It covers sports coverage, data sources, price semantics, contract restrictions, no-data behavior, and error conditions, leaving no caller-relevant ambiguity.

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?

The only parameter, event_id, is already fully documented in the schema with its source (list_events, query_events, or search results), and schema coverage is 100%. The description adds no additional parameter-level semantics because none are needed, so the baseline 3 applies.

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 opens with a specific verb-resource pair ('Get prediction-market game-line probabilities') and enumerates the supported sports, making the tool's purpose immediately identifiable. It also actively distinguishes itself from get_odds / GET /odds by stating it returns implied probabilities, not American odds, which separates it clearly from siblings.

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?

The description gives clear context for when this tool applies: prediction-market game-line contracts for specific sports, with explicit exclusions for non-game-line contracts and unsupported sports. It references get_odds as a different surface, but it does not explicitly say 'use X instead' for the alternatives, which keeps it just short of a 5.

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