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

Annotations already cover the safety profile (readOnly, idempotent, non-destructive, closed-world), so the description's job is to add behavior — and it does, disclosing the Pro entitlement gate and exactly which extra fields a paid account unlocks. It stops short of stating pagination, latency, or error behavior for bad game_id, which keeps it below a 5.

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 the usage trigger, then the return payload, then the prerequisite and the exclusion — a sensible ordering. The long semicolon-chained inventory of return fields is dense but each item is informative; only mild trimming would be possible.

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?

There is no output schema, so the description must describe returns itself, and it does comprehensively (probabilities, market lines, ATS form, leaders, injuries, and the Pro-only extras). Given the tool's complexity and three-parameter surface, an agent has everything needed to call it and interpret the result.

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%, so all three parameters are already documented, including the Pro requirement on include_breakdown. The description's only added param meaning is restating that game_id comes from tonight_slate or find_game, which the schema already says. Baseline 3 is appropriate when the schema carries the load.

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 ('who is favoured in one game, by how much, or how the two sides compare') and enumerates the concrete outputs (win probability, projected margin, spread/total, ATS form). An agent can distinguish this from head_to_head or props_research without opening any 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?

Opens with an explicit when-to-use trigger ('when the user asks who is favoured in one game'), states the prerequisite ('Needs a game_id from tonight_slate or find_game'), and names an exclusion ('Not for picks or betting advice'). That is when/when-not/prerequisite in one compact block.

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