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

Annotations already declare readOnlyHint=true and openWorldHint=true, so safety is covered. The description adds one behavioral note ('an empty source list is passed through'), which hints at empty-result handling but is phrased opaquely and gives no detail on ordering, pagination, or data freshness.

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 efficient sentences with the core operation front-loaded and the prerequisite second. The trailing 'an empty source list is passed through' is slightly cryptic but does not bloat the definition.

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 values need not be explained, and the description covers the operation and the key input dependency. What remains missing is guidance on choosing this tool over the other openligadb match-listing siblings, which keeps it from a 5.

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 all three parameters are already documented with the same semantics (season starting year, group_order_id matchday/round id, exact league shortcut). The description restates the parameter meanings without adding syntax or edge-case detail, so 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 states a specific verb and resource ('Return fixtures and results') and scopes it to one league, season, and matchday/round id. It implicitly separates itself from broad siblings like openligadb_league_matches by the matchday scoping, though it never names an alternative explicitly.

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?

It explicitly tells the agent how to obtain the required group_order_id ('Discover valid group_order_id values with openligadb_groups'), which is real routing guidance. It does not explain when to prefer this over openligadb_league_matches or openligadb_current_matchday, so no full 5.

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