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

Annotations only carry minimal flags (readOnlyHint=false, destructiveHint=false) and do not disclose behavioral nuances. The description adds valuable context that players see what is posted, explains that actorId shows a portrait, and that flavor acts as a subheading. No contradictions with annotations; both treat this as a mutable, non-destructive write operation.

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?

The description is four sentences, each earning its place: purpose, use cases, parameter guidance, and a critical visibility note. It is front-loaded with the core action and packs dense, useful information without fluff or repetition.

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 chat-send tool with 6 parameters all fully described in the schema, the description covers usage scenarios, formatting capabilities, parameter behaviors, and player visibility. It does not mention persistence or message length limits, but those are minor for correct invocation. The lack of an output schema is acceptable since the tool's return value is not critical to calling it.

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% with descriptions on every parameter, so the baseline is 3. The description exceeds this by providing concrete examples for flavor ('Narration', 'The Tavern'), explaining the @UUID link syntax, and clarifying that actorId overrides speaker and shows a portrait. This adds practical meaning beyond the raw 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?

The description opens with 'Send a message to the Foundry VTT chat log,' clearly stating the verb and resource. It then lists distinct use cases (narration, NPC dialogue, combat descriptions, out-of-character communication) which differentiates it from sibling chat tools like chat-list, chat-update, and chat-delete that manage existing messages.

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 description explicitly states when to use the tool: 'Use for narration, NPC dialogue, combat descriptions, and out-of-character communication with the player.' It provides clear context but does not name alternatives or exclusion criteria, so it stops short of a perfect 5.

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