React Native Expo MCP

by Divagnz

Overview Schema Source Related Servers Discussions Admin

TypeScript

Local

expo_build_local_start

Initiate a local native build for iOS or Android using Expo, with options for device, variant, and cache cleaning.

Instructions

Start local native build (expo run:ios or expo run:android)

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": {
      "platform": "<platform>"
    },
    "name": "expo_build_local_start"
  }
}

Input Schema

Name	Required	Description
`platform`	Yes	Platform to build for
`device`	No	Device name, ID, or "simulator"
`variant`	No	Build variant (default: debug)
`clean`	No	Clean build cache before building

Schema Changelog

Changes observed during successful MCP inspections.

First observedv0.0.1May 29, 2026

TDQS

B3.1/5.0

Behavior2/5

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

With no annotations provided, the description carries the full burden of behavioral disclosure. It only identifies the action as starting a local build, but does not explain that it may take significant time, require specific environment setup, or that it is a blocking operation. No side effects or resource implications are mentioned.

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

Conciseness4/5

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

The description is extremely concise: a single sentence that gets straight to the point. It is front-loaded with the essential purpose. Could potentially benefit from a bit more context, but no wasted words.

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

Completeness2/5

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

Given that there are 4 parameters, no output schema, and no annotations, the description is too minimal. It lacks context about when to choose local build vs cloud build, prerequisites (e.g., Expo CLI, development environment), and what the return status or output might be. The schema fills parameter details, but the overall picture is incomplete.

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% (all four parameters have descriptions). The tool description adds no additional meaning beyond the schema—it does not elaborate on parameter usage, defaults, or interactions. Hence, baseline score of 3 is appropriate.

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 'Start local native build' and specifies the underlying commands (expo run:ios or expo run:android). It effectively distinguishes the tool from siblings like expo_build_local_read and expo_build_local_stop, and from cloud builds (eas_build).

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 does not provide any guidance on when to use this tool versus alternatives (e.g., eas_build for cloud builds). There is no mention of prerequisites, context, or when not to use it.

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