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

Annotations already cover the read-only, idempotent, non-destructive profile, so the bar is lower. The description still adds real context: the library scope (stock + house content) and the default compact response shape with an opt-in for full descriptions.

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 front-loaded sentences with no waste: scope first, then use case, then the response-shape toggle. Every clause earns its place.

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 an output schema present and full parameter coverage, the description needn't explain return values. It completes the picture by stating which content is searchable and the default response shape, which is enough for correct invocation.

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 documents the `detail` enum thoroughly ('summary' vs 'full'), name matching, and pagination. The description largely restates the `detail` behavior and adds little parameter meaning beyond the schema, so 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?

States a specific verb+resource ('search the spell library') and pins down scope precisely: stock spells plus the user's own house spells. This distinguishes it cleanly from siblings like vault_get_spell (single fetch) and vault_search_items/rules.

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 a clear use case ('locate a spell or power by name, ruleset, or type') and routes to the full-detail mode. It stops short of naming the retrieval alternative (vault_get_spell) or stating when search is the wrong choice, so it's clear context but no explicit exclusions.

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