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

Annotations already declare readOnlyHint and openWorldHint, so safety is covered. The description adds genuinely behavioral detail beyond that: the source match is omitted from the returned list and two teams with no other meeting return an empty list, which sets correct expectations about result shape and edge cases.

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 core behavior, then requirements, then the empty-list caveat — a logical order. Slightly padded by re-listing all nine game values already present in the schema enum, which could be trimmed.

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?

Given four required params, full schema coverage, an output schema and read-only annotations, the description supplies everything an agent needs: what it returns, where IDs come from, and the empty-result edge case. No material gap remains.

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 four parameters are already documented, including the enum values for game and the 'match itself is left out' note. The description largely restates these; its only marginal addition is naming gosugamers_rankings as an additional ID source, which is small value over the schema.

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?

Specific verb ('Returns') plus a precisely scoped resource: the *other* meetings between two teams as seen from one match. It also enumerates the returned fields (tournament, start time, team ids/tags, scores, winner flags, URL), making it unmistakable versus siblings like gosugamers_match or gosugamers_team_results.

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?

Gives clear operational context: requires IDs sourced from gosugamers_matches, gosugamers_results or gosugamers_rankings, and notes the match_id is excluded from results. It stops short of naming an explicit alternative (e.g. team-vs-team history tools) or stating when not to use it, so it is strong but not a full when/when-not/alternative statement.

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