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

Annotations only cover the safety profile (readOnly=false, destructive=false, idempotent=false); the description adds the authorization model (owner or accepted gamemaster required) and rate-limit behavior (per-caller and per-campaign) that annotations cannot express. These are exactly the failure modes an agent needs to anticipate.

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, then permission, then rate limiting in descending order of importance. No sentence is filler and nothing is repeated from 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?

Moderate-complexity mutation with a rich schema and an output schema, so return values need no explanation. Purpose, permissions, failure mode, and rate limits are all covered; the only omitted detail is duplicate/already-member behavior, which is minor.

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% and the role enum is already documented with meaning for player/watcher/gamemaster, so the schema carries the parameter burden. The description adds nothing about individual parameters, which is the expected baseline when coverage is this high.

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: 'Send a campaign invite to another user.' Combined with the name, this is immediately distinguishable from the reciprocal sibling play_respond_to_campaign_invite and from play_send_friend_request; no ambiguity about the action performed.

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 the decisive precondition for use (caller must be the campaign's GM) and an explicit exclusion (players, watchers, and admins get 403), which tells an agent when this call will fail. It stops short of routing to alternatives (e.g. invite-by-email or friend-request flows), so it is clear context without full when-to-use guidance.

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