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

Annotations already cover idempotency and non-destructiveness, so the bar is lower. The description adds valuable behavioral context by explaining that existing canonical fields are attached automatically on first use and that explicit pre-attachment to subject types is allowed. It does not cover error behavior or permissions, but the added context is meaningful.

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 sentences, front-loaded with the core purpose, followed by a usage guardrail and a preference rule. Every sentence earns its place, and there is no filler or redundant wording.

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?

Despite strong usage guidance, the description omits all parameter semantics for a 5-parameter tool with a nested json_schema object and no output schema. An agent cannot reliably construct a valid call, especially the json_schema parameter, without additional information.

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?

With 0% schema coverage, the description must compensate but only gestures at subject_types and canonical_name through phrases like 'globally canonical field' and 'pre-attach to subject types.' The required json_schema remains completely unexplained, and aliases/description are never mentioned, so an agent must guess how to construct the payload.

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 action ('Register') on a specific resource ('a genuinely new globally canonical field') and contrasts it with pre-attaching to subject types. This distinguishes it clearly from siblings like register_subject_type_alias and makes the tool's scope unambiguous.

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?

Explicitly says not to ask routine confirmation for existing canonical fields because valid existing fields attach automatically on first use, and tells users to prefer raw_text for one-off narrative detail. This provides clear when-to-use and when-not-to-use guidance.

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