Plane MCP Server

create_milestone

Create a project milestone by specifying project ID and title, with optional target date and external references. Use this to track key project deadlines and deliverables.

Instructions

Create a new milestone.

Args: project_id: UUID of the project title: Milestone title target_date: Target date for the milestone (ISO 8601 format) external_source: External system source name external_id: External system identifier

Returns: Created Milestone object

Tool call template

Replace each placeholder with a value matching the input schema. Only required parameters are included; add optional parameters as needed.

{
  "id": 1,
  "jsonrpc": "2.0",
  "method": "tools/call",
  "params": {
    "arguments": {
      "project_id": "<project_id>",
      "title": "<title>"
    },
    "name": "create_milestone"
  }
}

Input Schema

Name	Required	Description	Default
`title`	Yes
`project_id`	Yes
`external_id`	No
`target_date`	No
`external_source`	No

Output Schema

Name	Required	Description	Default
`id`	No
`title`	Yes
`created_at`	No
`updated_at`	No
`external_id`	No
`target_date`	No
`external_source`	No

Schema Changelog

Changes observed during successful MCP inspections.

First observedv0.2.11Aug 7, 2026

TDQS

A3.6/5.0

Behavior2/5

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

No annotations are provided, so the description must disclose behavioral traits. It only states 'Create a new milestone' and returns a 'Created Milestone object,' with no mention of side effects, required permissions, validation rules, or project existence requirements. This is insufficient for a mutation tool.

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?

The description is a clean docstring with an Args list and Returns line. Every line provides necessary information without redundancy, and the structure is easy to scan. It is appropriately sized for the tool's simplicity.

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

Completeness4/5

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

With an output schema present, the description does not need to elaborate on return values. It covers all parameters, including required vs optional (implicitly via schema), and notes the ISO format for target_date. However, it lacks broader context such as when a milestone might be invalid or how it relates to projects, but this is not critical for a straightforward create tool.

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?

The description adds meaning to all five parameters in the Args section, e.g., 'project_id: UUID of the project' and 'target_date: Target date for the milestone (ISO 8601 format).' Since schema description coverage is 0%, this fully compensates by explaining each parameter's purpose and format, though some descriptions are terse (e.g., 'external_source: External system source name').

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 opens with 'Create a new milestone,' which is a specific verb+resource construction. It clearly distinguishes the tool from sibling CRUD tools like update_milestone, delete_milestone, list_milestones, and retrieve_milestone by the verb 'create.'

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

Usage Guidelines2/5

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 does not mention prerequisites, exclusions, or scenarios where another tool would be appropriate. Sibling tools such as create_work_item or create_cycle are undifferentiated.

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

Deploy Server