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

Annotations already establish read-only, idempotent, closed-world, non-destructive behavior. The description adds genuine value beyond them: the credential/auth requirement, the header alternative, and the security guarantee that credentials are never placed in URLs or echoed in errors.

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 tight sentences, front-loaded with the action and the timing constraint, then the auth mechanics. No filler and no repetition of the schema.

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 two-parameter, read-only tool with no output schema, this covers the key agent needs: when to call it, how to authenticate, and how the credential is handled. It stops short of describing what the 'assignment' object contains or the format rules for slug.

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 only 50% (slug has no description), so the description has to compensate, and it does: it clarifies that 'credential' is a private key supplied either as an argument or via an Authorization header. It adds little about the required 'slug' beyond what the schema pattern enforces.

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 ('Read the exact-version assignment and its Gameplay Contract'), so the core action is unambiguous. It does not, however, differentiate itself from the many nearby play_* siblings (start_play, prepare_play, play_state), so an agent still has to infer its place in the sequence.

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 an implied workflow cue ('before accepting a session'), which tells the agent roughly when this fires. It names no alternative tool and no condition that would select a sibling over this one, so usage is only implied rather than spelled out.

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