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

Annotations only declare the safety profile (non-read-only, non-idempotent, non-destructive, closed-world). The description adds genuinely new behavior: invites are single-use, expire in seven days, and are capped at three open invites, plus the auth mechanism. It stops short of describing the response or what single-use means in failure 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?

Two compact sentences, front-loaded with the action before the constraints and auth. The telegraphic, comma-spliced phrasing is efficient but slightly hurts readability; no wasted sentences.

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 no output schema and six parameters, the description covers the essentials an agent needs: auth method, lifetime, and invite cap. It omits the optional ref parameter and gives no hint of what a successful creation returns, but for a creation tool this is largely adequate.

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 already 83%, and the schema documents key, ref, game, mode and clock in far more detail than the description. The description restates the parameter list (game, mode, clock, label) and echoes the auth-header behavior, adding little beyond the schema. 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 — create a single-use private challenge — and names the key dimensions (game, mode, clock, label). It implicitly separates this from pit_invite_accept/pit_invite_cancel but never explicitly contrasts them, so it falls short of full sibling differentiation.

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?

The constraints 'Seven days, at most three open invites' tell the agent the operating limits but not when to choose this tool over pit_callout, pit_queue, or pit_play. No when-to-use or when-not-to-use guidance is given.

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