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

Annotations already declare readOnlyHint=true, idempotentHint=true, and destructiveHint=false, so the safety profile is covered. The description adds behavioral detail by specifying that the returned document includes nested abilities, requirements, ability score bonuses, and starting equipment references, going beyond the bare schema.

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 sentences, both functional: the first states the operation and result contents, the second gives the practical lookup workflow. There is no redundant phrasing or filler.

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 simple one-parameter getter with an output schema present and annotations covering safety, the description is complete. It identifies the resource, the necessary id, the included content, and how to obtain the id via vault_search_rules. No critical usage information is missing.

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 schema already defines id as the MongoDB `_id` of the vault document. The description merely says "by id," adding no new semantic information about the parameter. This matches the baseline for high schema coverage.

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 a specific verb and resource: "Fetch one rule document by id," which clearly distinguishes this from vault_search_rules (search/listing) and vault_create_rule/update_rule/delete_rule (mutations). It also enumerates the nested content included, leaving no ambiguity about what this tool returns.

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 gives an explicit workflow: "Pair with vault_search_rules to locate the id first." This tells the agent when this tool is appropriate after a search. It does not spell out when not to use it, but for a single-document fetch tool this is acceptable and clear context.

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