o3de-mcp

by nickschuetz

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Python

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start_build

Launch a CMake build in the background and obtain a build ID to poll for status.

Instructions

Start a CMake build in the background and return a build ID.

Unlike build_project, this returns immediately with a build ID that can be polled via get_build_status. Output is drained on a background thread to prevent pipe stalls on large builds.

Args: project_path: Path to the O3DE project. config: Build configuration -- profile, debug, or release (default: profile). target: Optional CMake target to build (default: all targets).

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_path": "<project_path>"
    },
    "name": "start_build"
  }
}

Input Schema

Name	Required	Default
`config`	No	profile
`target`	No
`project_path`	Yes

Output Schema

Name	Required	Description	Default
`result`	Yes

Schema Changelog

Changes observed during successful MCP inspections.

First observedv0.3.0Sep 5, 2026

TDQS

A4.8/5.0

Behavior4/5

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

Without annotations, the description carries the behavioral burden, and it does so well: it discloses the background execution, immediate return, pollable build ID, and background output draining to prevent pipe stalls. It does not mention error behavior or side effects beyond the build itself, but the core async behavior is clearly disclosed.

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 front-loaded with the core action and payoff, then adds a concise contrast with build_project and an Args section. Every sentence carries distinct information, and there is no repetition of schema fields in prose.

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 supplies the async workflow, the polling mechanism, pipe-stall prevention rationale, and parameter semantics. With an output schema available and no annotations, nothing needed to invoke the tool correctly is missing.

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

Parameters5/5

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

Schema description coverage is 0%, so the description must compensate, and it does: project_path is explained as the O3DE project path, config is given the allowed values profile/debug/release plus a default, and target is described as optional with a default of all targets. All three parameters receive meaning beyond the bare schema.

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 begins with a specific verb and resource: 'Start a CMake build in the background and return a build ID.' It differentiates itself from the sibling build_project by noting it returns immediately instead of blocking, so an agent can distinguish the tool without inspecting the schema.

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

Usage Guidelines5/5

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

It explicitly names build_project as the alternative and gives the deciding context: unlike build_project, this returns immediately with a pollable build ID. It also tells the agent how to follow up via get_build_status, making the intended async workflow clear.

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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