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

Goes well beyond the annotations by disclosing the one-save-per-session rule, the 2-hour expiry window, and that the stored duration is clamped to the session's real age. The only tension is that 'later saves are ignored' reads as idempotent while idempotentHint is false, though the differing response on a repeat call can reconcile this.

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?

Three short sentences, front-loaded with the action and constrained by lifecycle facts; there is no redundant or filler wording.

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?

For a mutation with nested parameters, the description covers lifecycle, idempotency, expiry, and duration clamping, and an output schema exists so return values need not be explained. The remaining gap is semantic guidance on the score, total_levels, and metrics payload.

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 0% and the description never mentions score, total_levels, metrics, or their nested fields (correct/wrong/skipped/played). Only duration_seconds gets indirect meaning through the cap statement, leaving most of the five parameters undocumented anywhere.

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 ('Saves the final result of a session') and ties it to the sibling that produces the session ('created by start_game_session'), which distinguishes it from get_game_results and start_game_session 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?

Implies the correct moment to call it (after a game session ends) and adds an operational rule ('Each session is saved once; later saves are ignored'). It does not explicitly say what to do if the session has already expired, but the practical context is clear.

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