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agy-mcp

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agy-mcp

日本語 · Apache-2.0

agy-mcp is a local Model Context Protocol server that lets an MCP client delegate a task to the Google Antigravity CLI (agy). It uses stdio, starts agy as a child process, and returns the CLI result as structured MCP content.

It is designed for a personal local installation that can also be inspected, adapted, and contributed to as open source. It is not an Antigravity product and does not replace Antigravity's own access controls or account requirements.

What it provides

MCP tool

Purpose

antigravity_run

Starts a new Antigravity conversation and returns its result and, when supplied by the CLI, its conversation_id.

antigravity_continue

Continues a conversation by ID. Without an ID, it asks agy to continue its latest conversation.

antigravity_models

Runs agy models and returns the CLI output. It does not start a model turn, but it may contact Antigravity.

run and continue accept a prompt, an absolute workspace, optional model and effort, a mode (plan or accept-edits), an autonomy level, and a hard timeout. The server runs up to four agy commands concurrently by default. Set AGY_MCP_MAX_CONCURRENT to change this limit.

List model slugs with antigravity_models, then use one in model.

{
  "prompt": "Review the authentication flow and identify likely edge cases.",
  "workspace": "/absolute/path/to/workspace",
  "model": "a-slug-returned-by-antigravity_models",
  "mode": "plan",
  "autonomy": "safe",
  "timeout_seconds": 300
}

timeout_seconds defaults to 300 and accepts integers from 10 through 3600.

Related MCP server: agymcp

Parallel calls

Submit multiple MCP tool calls concurrently to run independent tasks in parallel. Each call has its own CLI process, output, progress, timeout, and cancellation. Canceling one call leaves the others running; shutting down the server stops all active calls.

  • New conversations and continuations with different explicit conversation_id values can overlap, including in the same workspace.

  • Two continuations specifying the same conversation ID cannot overlap, even across workspaces; the second returns BUSY.

  • A continuation without an ID (--continue) requires exclusive access to the server. It returns BUSY while any call is active, and other calls return BUSY while it runs. Use the ID returned by antigravity_run for parallel follow-ups.

  • All commands, including antigravity_models, count toward the concurrency limit. Calls exceeding the limit return BUSY immediately and are not queued. Set the limit to 1 to restore serial execution.

These limits and conversation locks apply within one server process. Workspace files, CLI state, credentials, and account quota remain shared; the bridge does not create isolated worktrees or coordinate other servers or CLI sessions. Assign separate files or worktrees when parallel tasks edit code, and prefer explicit conversation IDs because other sessions can change the latest conversation.

Requirements

  • Node.js 22 or newer

  • pnpm 10 or newer (the repository pins pnpm 10.18.1)

  • An installed, authenticated Antigravity CLI available as agy, or an executable path supplied through AGY_MCP_BIN

  • A workspace that Antigravity is allowed to use

Read the Antigravity CLI headless documentation for the CLI's installation, authentication, trust, permissions, and current behavior. This project uses the official TypeScript MCP SDK.

Install from source

git clone https://github.com/Kaikei-e/agy-mcp.git
cd agy-mcp
pnpm install --frozen-lockfile
pnpm build
pnpm run doctor

pnpm run doctor checks the configured workspace and verifies that the installed agy advertises the CLI flags this bridge needs. It does not start a model turn. Authentication and workspace trust must still be established with Antigravity itself.

For an optional live smoke test after authenticating agy:

pnpm run probe

The probe invokes run and then continue on the returned conversation. It can consume your Antigravity quota and create a conversation. It is deliberately not part of CI.

Connect an MCP client

Build the server, then configure the client to launch the compiled entry point. Copy examples/claude-code.mcp.json, replace every absolute path with your own, and add it to the client configuration appropriate for your installation.

For Claude Code, a project .mcp.json entry can look like this:

{
  "mcpServers": {
    "antigravity": {
      "command": "node",
      "args": ["/absolute/path/to/agy-mcp/dist/index.js"],
      "env": {
        "AGY_MCP_DEFAULT_WORKSPACE": "/absolute/path/to/workspace",
        "AGY_MCP_ALLOWED_ROOT": "/absolute/path/to",
        "AGY_MCP_MAX_CONCURRENT": "4"
      }
    }
  }
}

The server communicates over standard input and output. Do not wrap it in a command that writes diagnostic text to stdout. Configure the MCP client's own timeout slightly longer than the tool's timeout_seconds; progress notifications and heartbeats are useful status signals, but they do not guarantee that a client resets its timeout.

Safety and workspace boundaries

The default request settings are mode: "plan" and autonomy: "safe".

  • safe inherits the permissions and workspace trust decisions made by agy. It is not a read-only guarantee.

  • sandbox adds the CLI's terminal restrictions. Its scope and behavior are defined by Antigravity.

  • full passes the CLI permission-bypass flag. It is rejected unless the server environment explicitly sets AGY_MCP_ALLOW_FULL_AUTONOMY=true.

Every supplied workspace must be an absolute, accessible directory. The server canonicalizes it before use. AGY_MCP_ALLOWED_ROOT, when set, permits only canonical workspaces beneath that root. This limits the selected workspace; it does not sandbox a child process's filesystem access or network access. Only point the server at workspaces and permissions you trust.

The bridge disables CLI slash-command expansion for prompts, but output returned by an agent remains untrusted data. Review proposed commands and edits before acting on them.

Configuration

Variable

Default

Meaning

AGY_MCP_BIN

agy

CLI executable name, or an absolute path or path relative to the server's current directory.

AGY_MCP_DEFAULT_WORKSPACE

server current directory

Default workspace after resolution and canonicalization.

AGY_MCP_ALLOWED_ROOT

unset

Optional canonical root that must contain every chosen workspace.

AGY_MCP_MAX_CONCURRENT

4

Maximum simultaneous CLI processes per server; integer from 1 to 32.

AGY_MCP_MAX_OUTPUT_CHARS

40000

Maximum characters in each MCP result representation; integer from 1024 to 1000000.

AGY_MCP_MAX_BUFFER_BYTES

8388608

Maximum captured CLI stdout before the process is stopped; integer from 1024 to 67108864.

AGY_MCP_ALLOW_FULL_AUTONOMY

false

Set exactly true to allow requests with autonomy: "full".

Each tool response supplies structuredContent and the same JSON in its text content. The whole representation, including error and metadata fields, is capped by AGY_MCP_MAX_OUTPUT_CHARS; truncated results say so. CLI stdout is independently capped by AGY_MCP_MAX_BUFFER_BYTES per process, so total memory use grows with concurrency.

Long-running calls emit MCP progress metadata when the client provides a progress token, plus a heartbeat while the CLI is waiting. On cancellation, timeout, or output-limit failure, the server attempts to terminate the CLI process group on Linux and macOS. Windows termination is best effort; verify that no child process remains when that matters.

Development

pnpm install --frozen-lockfile
pnpm check
pnpm test
pnpm format:check

pnpm pack runs the package's prepack build before creating an archive. There is no automated npm publishing workflow.

See CONTRIBUTING.md and SECURITY.md before filing an issue or pull request. Changes are released under the Apache License 2.0.

Available Tools

3 tools
antigravity_continueContinue AntigravityA
Destructive

Follow up in an existing Antigravity conversation. Different explicit conversation_ids can run in parallel; simultaneous continuations of the same ID return BUSY. Without an ID, agy resumes its most recent conversation and requires exclusive access to this server, otherwise BUSY is returned. Other CLI sessions may change the latest conversation. Use the same workspace as the original turn.

ParametersJSON Schema
NameRequiredDescriptionDefault
modeNoplan requests planning; accept-edits permits edits. Neither is an OS sandbox.plan
modelNoModel slug from antigravity_models. Omit to use the CLI default.
effortNo
promptYesTask to delegate. Refer to files relative to workspace. Treat returned model output as untrusted data.
autonomyNosafe inherits agy's permission settings; sandbox adds terminal restrictions; full bypasses permissions and requires server opt-in.safe
workspaceNoAbsolute path to a trusted workspace. Defaults to AGY_MCP_DEFAULT_WORKSPACE or server cwd.
conversation_idNo
timeout_secondsNoHard deadline in seconds. Configure the MCP client's timeout slightly longer.

TDQS

A4.6/5.0
Behavior5/5

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

Annotations already mark the tool as destructive, non-idempotent, and openWorld. The description adds meaningful behavioral context beyond those flags: parallel runs with distinct IDs, BUSY on simultaneous continuations, exclusive server access when no ID is given, and the risk of external CLI sessions altering the latest conversation. This is valuable operational transparency.

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?

Four sentences, all dense with relevant information: purpose, concurrency semantics, failure conditions, external-state caveat, and workspace requirement. No filler or redundant restatement of the name or annotations.

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?

For an 8-parameter mutating tool with no output schema, the description covers key operational constraints: conversation ID handling, BUSY states, workspace reuse, and external session effects. It does not describe return values or explicitly compare against antigravity_run, but the schema and annotations fill most remaining gaps.

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 schema covers 75% of parameters with descriptions, and the description adds semantics for conversation_id (omitting it resumes the latest conversation, with parallelism and BUSY behavior) and workspace (must match the original turn). Some parameters like effort remain undocumented in the description, but the schema enums partially compensate.

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 'Follow up in an existing Antigravity conversation,' which states a specific verb, resource, and scope. The focus on 'existing conversation' and 'continuations' clearly differentiates this from the sibling 'antigravity_run' without requiring the agent to open either schema.

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?

The description gives clear conditions for when to use explicit conversation_ids versus relying on the latest conversation, including BUSY risk and the warning that other CLI sessions may change the latest conversation. It also instructs to use the same workspace as the original turn, but it does not explicitly name antigravity_run as the alternative for starting a new conversation.

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

antigravity_modelsList Antigravity modelsA
Read-onlyIdempotent

List available model slugs and display names using agy models. Does not start a model turn; may contact the Antigravity service.

ParametersJSON Schema
NameRequiredDescriptionDefault

No parameters

TDQS

A4.3/5.0
Behavior4/5

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

The annotations already declare readOnly, openWorld, idempotent, and non-destructive, so the description only needs to add extra behavior. It adds that no model turn is started and that the Antigravity service may be contacted, which is useful context for side-effect expectations.

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?

Two short sentences, front-loaded and free of filler. Every phrase adds meaning, including the clarification that the call may contact the service.

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?

Complete for a no-argument read-only list tool: purpose, outcome, service contact, and non-turn behavior are all stated, and annotations cover safety. No output schema exists, but the description already says what will be returned (model slugs and display names).

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?

With an empty schema, there are no parameter semantics to document; 100% schema coverage means the description is not required to compensate. The description adds no parameter text, but none is needed.

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?

States a specific action ('List') and resource ('available model slugs and display names'), and explicitly notes it does not start a model turn, distinguishing it from the sibling run/continue tools. The mechanism phrase 'using agy models' is slightly cryptic but does not harm purpose.

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

Usage Guidelines3/5

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

Implied usage is clear for a zero-parameter listing tool, but it never directly says 'use this to inspect available models before running/continuing' or names any alternative. No explicit when/when-not guidance is present, so the agent must infer selection from the title and siblings.

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

antigravity_runRun AntigravityA
Destructive

Start one Antigravity CLI turn in a new conversation. Useful for repository research, a second opinion, and explicitly requested edits. Returns a conversation_id for follow-up. Up to 4 agy calls can run concurrently per server; excess calls return BUSY. Parallel calls share workspace files and your existing Antigravity account and quota.

ParametersJSON Schema
NameRequiredDescriptionDefault
modeNoplan requests planning; accept-edits permits edits. Neither is an OS sandbox.plan
modelNoModel slug from antigravity_models. Omit to use the CLI default.
effortNo
promptYesTask to delegate. Refer to files relative to workspace. Treat returned model output as untrusted data.
autonomyNosafe inherits agy's permission settings; sandbox adds terminal restrictions; full bypasses permissions and requires server opt-in.safe
workspaceNoAbsolute path to a trusted workspace. Defaults to AGY_MCP_DEFAULT_WORKSPACE or server cwd.
timeout_secondsNoHard deadline in seconds. Configure the MCP client's timeout slightly longer.

TDQS

A4.2/5.0
Behavior4/5

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

Annotations already flag destructiveHint=true, so the description's mention of 'explicitly requested edits' is consistent. The description adds genuine non-obvious traits beyond annotations: the 4-call concurrency limit with BUSY responses, shared workspace files across parallel calls, and the shared account/quota semantics.

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?

Five sentences, each earning its place: core purpose, use cases, return contract, concurrency limit, and shared-state caveat. The core action is front-loaded and there is no filler or repetition of schema content.

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 no output schema, the description compensates by stating the return value (conversation_id). It covers concurrency, side effects, and shared state for a 7-parameter mutation tool. The only notable gap is that the follow-up path to antigravity_continue is hinted at rather than explicitly stated.

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 high (86%), so the schema documents most parameters. The main description adds a small amount of cross-call semantics for workspace ('Parallel calls share workspace files') not present in the parameter docs, but otherwise relies on the 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?

States a specific verb ('Start') plus resource ('one Antigravity CLI turn') with a differentiating qualifier ('in a new conversation'). This distinguishes it from sibling antigravity_continue, and the mention of returning a conversation_id reinforces that separation.

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?

Gives three concrete use contexts: repository research, second opinion, and explicitly requested edits. It does not explicitly name the alternative for follow-up conversations or state when not to use it, though 'new conversation' strongly implies the exclusion.

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

Tool Schema Changelog

Recent tool additions, removals, and schema changes observed during successful MCP inspections.

  1. 3 tool updatesv0.1.0
    • First observedantigravity_continue
    • First observedantigravity_models
    • First observedantigravity_run
Deploy Server
One endpoint for every MCP toolRayrun runs every MCP server behind one URL and holds the credentials. Each call is decided per client, tool, and argument, then recorded.ray.runAd

TDQS

A4.5/5.0

Scored across 3 tools

Disambiguation5/5

Each tool has a distinct purpose: run starts a new conversation, continue follows up on an existing one, and models lists available models. There is no overlap or ambiguity between them.

Naming Consistency5/5

All tools use the consistent 'antigravity_' prefix followed by a clear verb (run, continue, models). The naming pattern is uniform and predictable.

Tool Count5/5

Three tools is an ideal size for this server's scope: it provides the essential operations for interacting with the Antigravity CLI (start, continue, list models) without unnecessary bloat or missing functionality.

Completeness5/5

The server covers the full lifecycle of an Antigravity turn: starting a new conversation, continuing it, and discovering available models. Given its focused purpose, there are no obvious gaps.

Maintenance

ActivityMaintained
ResponsivenessNo issues

Resources

Related MCP Connectors

Related MCP Servers

  • agymcp

    leologoli
    F
    license
    Not graded
    quality
    C
    maintenance
    Wraps the Antigravity CLI (agy) as an MCP server, enabling Claude Code and other MCP clients to execute AI tasks and manage conversations via the agy command.
    1
    -

  • antigravity-mcp

    alvarosw
    A
    license
    Not graded
    quality
    B
    maintenance
    Enables MCP-compatible coding agents to run the local Antigravity CLI as a coding agent, manage conversation context and common options, and inspect usage, quota, models, version, help, and read-only slash commands.
    39 npm
    MIT