Completions

Completions provide real-time autocomplete suggestions for tool parameters. Instead of memorizing project IDs, branch names, or user logins, you type a few characters and the server queries GitLab for matches.

The problem

Without completions:
  User: "Create issue in project..." → What's the ID? → Must call list_projects first

With completions:
  User types: "mcp" → Server suggests: "gitlab-mcp-server (1835)", "redmine-mcp-server (1869)"

This transforms a multi-step lookup into a single, interactive selection.

How it works

sequenceDiagram
    participant U as User
    participant AI as AI Assistant
    participant S as MCP Server
    participant GL as GitLab API

    U->>AI: Starts typing argument value
    AI->>S: completion/complete (arg: "project_id", value: "mcp")
    S->>GL: GET /projects?search=mcp
    GL-->>S: Matching projects
    S-->>AI: Completion suggestions
    AI->>U: Shows dropdown with options

Supported argument types

The server supports 17 completion argument types organized into global and per-project completers:

Global completers

These work without a project context:

Argument	Completes	Example
`project`	Project names/paths	`my-group/my-project`
`group`	Group names/paths	`engineering`
`user`	User names/logins	`john.doe`
`namespace`	Namespaces (groups + users)	`my-group`

Per-project completers

These require a project context and search within that project:

Argument	Completes	Example
`branch`	Branch names	`feature/login`
`tag`	Tag names	`v1.2.0`
`milestone`	Milestone titles	`Sprint 14`
`label`	Label names	`priority::high`
`merge_request`	MR titles/IIDs	`!42 Fix login`
`issue`	Issue titles/IIDs	`#100 Bug report`
`pipeline`	Pipeline IDs	`12345`
`environment`	Environment names	`production`
`release`	Release tag names	`v2.0.0`
`wiki_slug`	Wiki page slugs	`getting-started`
`version`	Version/milestone IDs	`v1.0`
`runner`	Runner descriptions	`shared-runner-1`
`board`	Board names	`Development`

How completions improve AI accuracy

Completions reduce errors in several ways:

Eliminates typos — Users select from validated suggestions instead of typing exact values
Reduces round-trips — No need to call list_projects before create_issue
Provides context — Suggestions include IDs alongside names, ensuring correct values
Real-time search — Results update as the user types, powered by GitLab’s search API