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

Annotations already declare readOnly, idempotent, non-destructive and closed-world, so the safety profile is covered. The description adds genuinely non-obvious behavior: results are ordered newest first, and each call "costs 1 credit" — a billing constraint the agent cannot learn from any structured field.

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?

Four short sentences, front-loaded with the primary use case, then return shape, then filters, then cost. No filler and nothing buried — the credit cost is placed last where it reads as a caveat rather than a headline.

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 prose beyond the brief field summary given. All five parameters are documented in the schema, the safety profile is in annotations, and cost plus sort order are stated — nothing an agent needs to call this correctly is missing.

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 description coverage is 100%, so limit, league, offset, season and status are all documented in the schema itself. The description only echoes season and status and adds no syntax or interaction detail beyond what the schema states ("Year, e.g. 2025"), 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 gives a specific verb and resource ("lists events") and enumerates what comes back (venue, status, number of fights, main event), which is concrete enough to picture the response. "Use to find cards" plus the sibling set (get_event, get_schedule) leaves a small ambiguity about discovery vs. single-record retrieval, but the plural list framing disambiguates well enough.

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?

"Use to find cards" implies the browse/discovery use case and the filter note tells the agent it can narrow by year and completion status. However, no alternative is named — nothing says when to prefer get_event or get_schedule over this tool — so the agent must infer routing from the sibling names.

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