List custom field definitions for a specific entity category and optional sub-category (e.g. PRINT + PRINT_QUEUE for queue-item custom fields).
| Name | Required | Description | Default |
|---|---|---|---|
| category | Yes | ||
| subCategory | No | ||
| includeDisabled | No |
Changes observed during successful MCP inspections.
Input schema / properties / subCategory / enumPrevious value: -[
- "print_queue",
- "print_job",
- "user_file"
-]New value: +[
+ "print_queue",
+ "print_job",
+ "user_file",
+ "user_file_printable",
+ "user_file_non_printable",
+ "user_file_vector"
+]Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
Annotations already declare read-only, idempotent, and non-destructive behavior. The description adds that it returns 'definitions' and supports filtering, which is useful context. However, it does not describe pagination, ordering, or any response details, which would further aid the agent.
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 a single, tight sentence that packs the core purpose, filtering behavior, and an example without any fluff or redundancy. It is well-structured and front-loaded with the key information.
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 read-only list tool with strong annotations, the description is fairly complete. It explains the tool's niche (entity-scoped definitions) and gives an example. Given the absence of an output schema, the description adequately covers the essential context an agent needs to decide when to call 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?
The description explains 'category' and 'subCategory' with an example, but it does not explicitly describe the 'includeDisabled' parameter or the meaning of all enum values. The schema provides enums but no per-field descriptions, so the description only partially covers parameter semantics.
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 clearly specifies a verb ('List'), a resource ('custom field definitions'), and a distinguishing filter ('for a specific entity and optional sub-category'). The example (PRINT + PRINT_QUEUE) makes it unambiguous and differentiates it from the sibling list_custom_fields tool.
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?
It implicitly conveys when to use this tool — when you need custom fields scoped to an entity/sub-category rather than all custom fields. The example provides concrete guidance, though it doesn't explicitly contrast with list_custom_fields or mention alternatives.
Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.
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