Mailrith Email Marketing

List custom fields

custom_fields_list

Read-onlyIdempotent

Returns a bounded page of custom fields in the authenticated workspace, including each field's exact ready-to-use email personalization token. Permission: custom_fields:read. Pagination: use bounded pages and returned cursors. API reference: https://mailrith.com/developers/api-reference.

Tool call template

This tool declares no required parameters. Add optional parameters from the input schema as needed.

{
  "id": 1,
  "jsonrpc": "2.0",
  "method": "tools/call",
  "params": {
    "arguments": {},
    "name": "custom_fields_list"
  }
}

Input Schema

Name	Required	Description
`limit`	No	Maximum number of custom fields to return.
`search`	No	Filter custom fields by label or type.
`starting_after`	No	Use the opaque cursor from the previous page to request the next page.

Output Schema

Name	Required	Description
`error`	No
`response`	No
`request_id`	Yes	The stable correlation ID for this MCP tool invocation.
`operation_id`	Yes	The stable Mailrith public API operation ID.

Schema Changelog

Changes observed during successful MCP inspections.

AddedSep 3, 2026
RemovedSep 3, 2026
AddedAug 17, 2026

TDQS

A4.3/5.0

Behavior4/5

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

Annotations already declare readOnly, idempotent, and non-destructive. The description adds valuable behavioral context: 'bounded page', cursor-based pagination, required permission 'custom_fields:read', and the inclusion of personalization tokens. This goes beyond mere read-only hints.

Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

Conciseness5/5

Is the description appropriately sized, front-loaded, and free of redundancy?

Three tightly structured sentences cover function, permission, and pagination, with a reference link. Every sentence earns its place; no fluff or redundancy.

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Completeness5/5

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

Given rich annotations, full schema description, and the presence of an output schema, the description covers all necessary aspects: purpose, permission, pagination behavior, and the distinctive token inclusion. Complete for a list operation.

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Parameters3/5

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

Schema description coverage is 100%, with clear descriptions for limit, search, and starting_after. The description adds the concept of 'bounded page' and returned cursors, which reinforces starting_after's purpose but does not introduce new parameter-level detail.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Purpose5/5

Does the description clearly state what the tool does and how it differs from similar tools?

The description clearly states the verb 'Returns' with the specific resource 'custom fields' and the scope 'in the authenticated workspace'. It also highlights the unique value (ready-to-use email personalization tokens), distinguishing it from the sibling custom_fields_get.

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Usage Guidelines4/5

Does the description explain when to use this tool, when not to, or what alternatives exist?

Provides clear context for when to use: listing custom fields with pagination and required permission. It does not explicitly name alternatives or exclusions, but the sibling custom_fields_get makes the list-vs-get distinction implicit.

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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