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

Annotations already declare readOnly/idempotent/non-destructive, so safety is covered. The description adds genuinely useful behavior the annotations cannot convey: coverage is per-competition and an uncovered match returns found:false with a reason rather than throwing, which tells the agent how to interpret a miss.

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?

Two tight sentences, front-loaded with what the tool returns, then the one non-obvious behavioral caveat. No filler or restated title.

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 no output schema, the description usefully enumerates the returned fields and the found:false failure shape, which is what an agent needs to consume the result. Minor gap: no pagination or multi-match guidance, though for a single-match lineup tool that is a small omission.

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% and the schema already documents both event_id (idEvent format) and _apiKey (free tier vs supporter key). The description adds no syntax or format detail beyond the schema, 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?

Names the specific resource (starting eleven and substitutes for one match) and the exact per-player payload (position, squad number, TheSportsDB player id). This clearly separates it from event_detail, event_timeline, and event_stats without needing their 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?

The description implies the use case (fetch a lineup for a given match) but never states when to pick this over siblings like event_detail or event_timeline. The coverage note tells the agent what a miss looks like, not when to reach for this tool instead of another.

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