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

Annotations already declare readOnlyHint=false, destructiveHint=false, idempotentHint=false and openWorldHint=false, so the safety profile is covered structurally. The description adds a valuable prerequisite workflow (read metadata before creating) but says nothing about side effects on the live registration form, whether duplicate names are rejected, or whether the field goes live immediately. Useful addition, but not rich behavioral disclosure.

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 action and followed by the prerequisite and the routing rule. The default-field enumeration is long but functional rather than filler; nothing is redundant.

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 an 11-parameter mutation with nested objects, the description covers purpose, precondition and correct alternative, and an output schema exists so return values need no explanation. What's missing is guidance on the complex optional parameters (config, dependency, options vs session_ids) that the schema only partially documents.

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 64% and 11 parameters exist, so several (config, position, dependency, ticket_type_ids) are undocumented in both schema and description. The description's main contribution is semantic: it defines which names are reserved default fields, which meaningfully constrains the required `name` parameter. That is real added value, but it does not compensate for the remaining gaps.

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 (create), resource (additional user field) and scope (the provided event's default registration flow). It also names the sibling it must not be confused with (update_default_user_field) and enumerates the reserved default field names, so the agent can distinguish it from related tools without opening a schema.

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 an explicit pre-flight step (check registration metadata default_fields and existing additional_fields) and a hard routing rule: if the requested name matches a default field, use update_default_user_field instead. This is exactly the when-to-use/when-not-to-use/alternative structure that scores top marks.

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