dex_list_custom_fields

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

No annotations are provided, so the description carries the full burden of behavioral disclosure. It states this is a retrieval operation, implying it's read-only, but doesn't cover critical aspects like authentication needs, rate limits, error conditions, or response format (e.g., pagination, sorting). For a tool with zero annotation coverage, this is a significant gap in transparency.

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 two sentences with zero waste. The first sentence directly states the tool's purpose, and the second adds useful context about custom fields without redundancy. It's appropriately sized and front-loaded, making it easy for an agent to parse quickly.

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?

Given the tool's simplicity (0 parameters) but lack of annotations and output schema, the description is incomplete. It doesn't explain what the retrieval returns (e.g., a list of field objects with properties like name, type), potential limitations (e.g., max fields), or behavioral traits. For a tool that likely returns structured data, more context is needed to guide the agent effectively.

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 tool has 0 parameters, and schema description coverage is 100% (though trivial for an empty schema). The description adds no parameter information, which is appropriate here. A baseline of 4 is applied for zero-parameter tools, as there's nothing to document beyond what the schema already indicates (no inputs required).

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 states the verb ('Retrieve') and resource ('all custom field definitions'), making the purpose specific and understandable. It adds helpful context about what custom fields are ('allow adding structured data to contacts beyond the built-in fields'), which distinguishes it from general field-related tools. However, it doesn't explicitly differentiate from sibling tools like dex_update_custom_field or dex_delete_custom_field, preventing a perfect score.

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 provides no guidance on when to use this tool versus alternatives. It doesn't mention prerequisites (e.g., whether custom fields must exist), compare it to other listing tools (e.g., dex_list_contacts), or specify use cases (e.g., for reference before creating/updating fields). This leaves the agent with minimal context for selection.

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