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Mailercloud

by com.mailercloud.mcp
OverviewDiscussionsAdmin

create_custom_field

Create a custom contact field (property). name 3-30 characters; type text, number, date or textarea (fixed once created); optional description. Accounts can have up to 100 custom fields. Set dry_run: true to preview.

Input Schema

NameRequiredDescriptionDefault
nameYesField name, 3-30 characters
typeYestext, number, date or textarea. Cannot be changed later
dry_runNoValidate and show what would be created without creating anything
descriptionNoOptional description, 3-500 characters

Schema Changelog

Changes observed during successful MCP inspections.

  1. Changed3 schema fields changed
    • changedInput schema / properties / name / description
      Previous value: -"Field name, 3-30 characters,required"New value: +"Field name, 3-30 characters"
    • changedInput schema / properties / type / description
      Previous value: -"text, number, date or textarea. Cannot be changed later,required"New value: +"text, number, date or textarea. Cannot be changed later"
    • addedInput schema / properties / type / enum
      Added value: +[
+  "text",
+  "number",
+  "date",
+  "textarea"
+]
  2. Added

TDQS

A4.7/5.0
Behavior5/5

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

The description adds vital operational context beyond the annotations, specifically the business rule that a field's type is immutable ('fixed once created') and the system capacity limit ('Accounts can have up to 100 custom fields').

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?

All necessary information—naming rules, type limitations, capacity limits, and dry run usage—is packed into a single, highly efficient paragraph without 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?

The description is exceptionally complete, covering all operational constraints (field limits, character counts), behavioral constraints (type immutability), and operational features (dry run).

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

Parameters4/5

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

Although the schema provides 100% coverage, the description uses the parameter details to reinforce constraints (3-30 characters for name) and critical behavioral semantics (type immutability) which helps the agent validate input quality against the tool's business logic.

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 ('Create'), the resource ('custom contact field'), and its specific nature ('property'). It is unambiguously distinct from 'update_custom_field' and 'list_custom_fields'.

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?

It provides clear guidance on how to use the 'dry_run' parameter for preview. Furthermore, stating that the type is 'fixed once created' is crucial context for when not to expect a successful modification later.

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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