Await Until MCP Server

A Model Context Protocol (MCP) server that provides polling/waiting primitives. Repeatedly checks conditions (shell commands, HTTP endpoints, files, or other MCP tools) at configurable intervals until they're met or time out.

Features

• Command Polling: Execute shell commands until output matches a condition
• URL Polling: Poll HTTP endpoints until they return expected status/body
• File Polling: Watch filesystem until files exist, disappear, or contain content
• MCP Polling: Call any other MCP server's tool and poll until the result matches — auto-discovers servers from your mcp.json (Kiro, Cursor, Claude Desktop)
• Configurable: Interval, timeout, and match conditions for every tool
• MCP Protocol: Communication via stdio transport
• TypeScript: Fully typed with Zod validation
• No Configuration: No environment variables required

Architecture

Agent calls await_until_* tool
  → Await-Until MCP Server starts polling loop
    → Each iteration: execute check (command/url/file/mcp)
    → Evaluate match condition against output
    → If matched → return success
    → If not → sleep interval → retry
    → If timeout → return failure

For await_until_mcp, the server reads your IDE's mcp.json config, spawns the target MCP server as a child process via stdio, calls the specified tool, and evaluates the result.

Usage

# Development
pnpm dev

# Production
pnpm build
node dist/index.js

Available MCP Tools

await_until_command

Repeatedly executes a shell command at a given interval until the output matches a condition or times out.

Parameters:

• command (string): Shell command to execute on each poll
• match (string, optional): How to evaluate output (default: exists)
  • exists: Exit code is 0
  • contains: stdout contains the pattern
  • not_contains: stdout does NOT contain the pattern
  • equals: stdout exactly equals the pattern (trimmed)
  • not_equals: stdout does NOT equal the pattern
  • regex: stdout matches the regex pattern
  • not_empty: stdout is not empty
• pattern (string, optional): String or regex to match. Required for contains, not_contains, equals, not_equals, regex
• interval_seconds (number, optional): Seconds between polls (default: 5, min: 1, max: 300)
• timeout_seconds (number, optional): Max seconds to wait (default: 120, min: 1, max: 3600)
• cwd (string, optional): Working directory for the command
• shell (string, optional): Shell to use (default: /bin/bash)

Example — wait for a service to be healthy:

{
  "command": "curl -sf http://localhost:3000/health",
  "match": "contains",
  "pattern": "\"status\":\"ok\"",
  "interval_seconds": 5,
  "timeout_seconds": 60
}

Example — wait for a Docker container to be running:

{
  "command": "docker inspect -f '{{.State.Running}}' my-container",
  "match": "equals",
  "pattern": "true",
  "interval_seconds": 3,
  "timeout_seconds": 30
}

await_until_url

Polls an HTTP endpoint at a given interval until it returns the expected status code and/or body content.

Parameters:

• url (string): URL to poll
• method (string, optional): HTTP method — GET, POST, or HEAD (default: GET)
• expected_status (number, optional): Expected HTTP status code. If omitted, any 2xx is accepted
• body_contains (string, optional): String that the response body must contain
• headers (object, optional): Custom headers to send
• interval_seconds (number, optional): Seconds between polls (default: 5)
• timeout_seconds (number, optional): Max seconds to wait (default: 120)

Example — wait for an API to be ready:

{
  "url": "http://localhost:4000/api/health",
  "expected_status": 200,
  "interval_seconds": 5,
  "timeout_seconds": 90
}

await_until_file

Polls the filesystem at a given interval until a file exists, disappears, or contains expected content.

Parameters:

• path (string): Absolute or relative file path to watch
• match (string, optional): Condition to check (default: exists)
  • exists, not_exists, contains, regex, not_empty
• pattern (string, optional): String or regex to match. Required for contains, regex
• interval_seconds (number, optional): Seconds between polls (default: 3)
• timeout_seconds (number, optional): Max seconds to wait (default: 120)

Example — wait for a build artifact:

{
  "path": "./dist/index.js",
  "match": "exists",
  "interval_seconds": 3,
  "timeout_seconds": 120
}

Example — wait for a lock file to be removed:

{
  "path": "/tmp/migration.lock",
  "match": "not_exists",
  "interval_seconds": 5,
  "timeout_seconds": 300
}

await_until_mcp

Polls another MCP server's tool at a given interval until the result matches a condition or times out. Reads your IDE's mcp.json config to discover and spawn the target MCP server, then calls the specified tool repeatedly.

How it works:

1. Reads mcp.json from your workspace or global config (auto-detects Kiro, Cursor, Claude Desktop)
2. Finds the server config by server_name
3. Spawns the MCP server as a child process via stdio
4. Calls tool_name with tool_arguments on each poll
5. Evaluates the text result against the match condition
6. Returns when matched or timed out

Parameters:

• server_name (string): Name of the MCP server as defined in your mcp.json (e.g. datadog, slack, arvore-mysql)
• tool_name (string): Name of the MCP tool to call on each poll (e.g. search_logs, query)
• tool_arguments (object, optional): Arguments to pass to the MCP tool on each call
• match (string, optional): How to evaluate the result (default: not_empty)
  • contains, not_contains, equals, not_equals, regex, not_empty
• pattern (string, optional): String or regex to match. Required for contains, not_contains, equals, not_equals, regex
• interval_seconds (number, optional): Seconds between polls (default: 10)
• timeout_seconds (number, optional): Max seconds to wait (default: 120)
• mcp_config_path (string, optional): Explicit path to mcp.json. Auto-detected if omitted

Config auto-detection order:

1. mcp_config_path (if provided)
2. .kiro/settings/mcp.json (workspace)
3. .cursor/mcp.json (workspace)
4. .vscode/mcp.json (workspace)
5. ~/.kiro/settings/mcp.json (global)
6. ~/.cursor/mcp.json (global)
7. ~/Library/Application Support/Claude/claude_desktop_config.json (global)

Example — wait for a database row to appear:

{
  "server_name": "arvore-mysql",
  "tool_name": "query",
  "tool_arguments": {
    "sql": "SELECT status FROM migrations WHERE name = 'add_users_table'"
  },
  "match": "contains",
  "pattern": "completed",
  "interval_seconds": 5,
  "timeout_seconds": 300
}

Example — wait for a LaunchDarkly flag to be enabled:

{
  "server_name": "launchdarkly",
  "tool_name": "get_flag",
  "tool_arguments": {
    "key": "new-checkout-flow",
    "environment": "production"
  },
  "match": "contains",
  "pattern": "\"on\":true",
  "interval_seconds": 10,
  "timeout_seconds": 120
}

Example — wait for a Datadog monitor to recover:

{
  "server_name": "datadog",
  "tool_name": "list_monitors",
  "tool_arguments": {
    "name": "API Latency",
    "groupStates": ["Alert"]
  },
  "match": "contains",
  "pattern": "\"overall_state\":\"OK\"",
  "interval_seconds": 30,
  "timeout_seconds": 600
}

MCP Configuration

{
  "mcpServers": {
    "await-until": {
      "command": "npx",
      "args": ["-y", "@arvoretech/await-until-mcp"]
    }
  }
}

Development

pnpm install
pnpm dev
pnpm build
pnpm lint

License

MIT