Tools for building, testing and running MCP servers
Writing an MCP server takes an afternoon. Running one that agents can rely on takes more. NitroStack and Karada build and host servers, from code or straight from an OpenAPI spec. Pomerado makes one out of a website. Bifrost routes MCP tools behind a gateway. CATT and Gauge CLI point real agents at your server to see what breaks. MCP Census vets someone else's server before you install it, MELRA polices the tool calls, and Agentic Resource Registry gives your team one place to share the servers that work. 9 tools, in the order they appear in the directory. This is not a ranking.
Grouped by job: Agent Safety & MCP Security · MCP Servers & Tools
Bifrost
Open-source (Apache-2.0) AI gateway from Maxim AI: one OpenAI-compatible API for thousands of models with failover, load balancing, semantic caching, virtual keys, budgets and an MCP gateway; Enterprise plan available.
Gauge CLI
Open-source (MIT) CLI that runs real coding agents against your Skills, CLIs, SDKs, MCP servers and docs, captures where they get stuck and lets your own agent test fixes locally in Docker; part of the Gauge agent-led growth platform.
Pomerado
Turns any website, from consumer sites to legacy portals, into a hosted API or MCP server for your agents, faster and more reliable than browser agents; open source and backed by Y Combinator.
NitroStack
Full-stack MCP platform: open-source TypeScript and Python SDKs, an MCP CLI, the NitroStudio desktop app for testing and debugging, and NitroCloud managed hosting for production MCP servers and apps.
Karada.ai
Infrastructure for MCP: auto-compile APIs into Go MCP servers, keep tools in sync with CI/CD on every deploy, add composable plugins and multiplex everything behind one gateway; free Hobby plan, Pro from $19/month.
The MCP Census
Checks public evidence for an MCP server and returns PASS, REVIEW, BLOCK or UNKNOWN before you install or call it; lookup, preflight, whole .mcp.json config audits, a change feed, REST API and its own MCP endpoint, no account needed for stats.
MELRA
Open-source local MCP runtime that checks AI-agent tool calls against policy, gates risky actions on approval, verifies results and parks uncertain outcomes instead of blindly retrying after timeouts. Alpha; AGPL-3.0, SDKs Apache-2.0.
CATT
Consumer Agent Testing Tool: open-source (MIT) Python CLI that runs a scripted or model-driven surrogate assistant (Muse or Instinct emulation, unaffiliated) against your MCP server, MCP app, website or HTTP API, checks what the service actually did and records sealed evidence you can replay and diff in CI.
Agentic Resource Registry
Self-hosted, open-source (Apache-2.0) registry for sharing a team's coding agent resources (skills, agent files, MCP servers) with usage insights; works with Claude Code, Kiro, Cursor, Codex, Pi and more through the observal CLI. Formerly Observal.
What it does for MCP, where it runs, what it costs.
Straight from each vendor's own pages. Plans move often, so the check date is below.
| Tool | What it does | Runs on | Open source | Price |
|---|---|---|---|---|
| Bifrost | AI gateway with an MCP gateway built in: connects tool servers, allow-lists tools per virtual key, and Code Mode chains several tools in one run. | Self-hosted: Docker, Kubernetes or a Go binary. | Yes, Apache-2.0. | Open source is free. Enterprise is custom, with a 14-day trial. |
| Gauge CLI | Runs real coding agents against your SDK, CLI, docs or MCP server and records where they get stuck. | Your machine, in Docker, on your own Claude Code or Codex subscription. | Yes, the CLI is MIT. | CLI free, no Gauge account. Hosted Gauge starts with 1,000 free credits. |
| Pomerado | Turns a website, logins included, into a hosted API or MCP tool for your agent. | Hosted MCP server. | Core harness is MIT on GitHub. The service is hosted. | Free: 100 tool calls a day, 10 new integrations a month. Premium $50/mo. |
| NitroStack | TypeScript SDK and CLI for MCP servers and apps, NitroStudio to test them, NitroCloud to host them. | SDK and Studio on your machine. NitroCloud deploys from GitHub and scales to zero. | SDK, CLI and widgets are Apache-2.0. NitroStudio and NitroCloud are commercial. | Free to start, no card. No NitroCloud prices published. |
| Karada.ai | Compiles an OpenAPI spec or Postman collection into a Go MCP server, recompiles when the spec changes, and puts your servers behind one gateway. | Hosted. Bring your own Streamable HTTP server if you have one. | No license stated. Hosted. | Hobby free: 5 servers, 100,000 requests a month. Gateway Pro $19/mo. All-Access Pro $49/mo. |
| The MCP Census | Checks public evidence for an MCP server and returns PASS, REVIEW, BLOCK or UNKNOWN. Audits a whole .mcp.json. | Website, REST API and its own MCP endpoint. | No license stated. Hosted. | 10 lookups a day with no key. Free key: 1,000 credits a month. Builder $19/mo, Team $49/mo. |
| MELRA | Sits between agent and tools: checks each call against policy, asks before risky ones, verifies results and parks unclear outcomes instead of retrying. | macOS, Linux and Windows, Node.js 22.13 or newer. Any MCP client, including Claude Code, Codex and Cursor. | Yes, AGPL-3.0. SDKs are Apache-2.0. | Free. Alpha. |
| CATT | A scripted or model-driven stand-in assistant uses your MCP server or MCP app, then CATT checks what the service actually did and seals the evidence. | Python 3.12+ CLI with Node.js 20+. Release evidence covers macOS. | Yes, MIT. | Free. No paid plan listed. |
| Agentic Resource Registry | Self-hosted registry where a team publishes, reviews and installs MCP servers, skills and agent files, with usage data. | Your own servers. observal CLI for Claude Code, Cursor, Kiro, Codex, Pi and more. | Yes, Apache-2.0. | Free. No paid plan listed. |
Checked 2026-10-31. Sources: Bifrost pricing, Bifrost on GitHub, Gauge for coding agents, Pomerado, Pomerado on GitHub, NitroStack, NitroStack on GitHub, Karada pricing, MCP Census API, MELRA on GitHub, CATT on GitHub, Agentic Resource Registry on GitHub.
Pick it if.
- BifrostYou already need an LLM gateway and want MCP tools governed in the same place, self-hosted.
- Gauge CLIYou ship an SDK or MCP server and want to watch Claude Code and Codex try to use it.
- PomeradoThe tool your agent needs is a website with no API, maybe behind a login.
- NitroStackYou write your own MCP server in TypeScript and want SDK, test bench and hosting from one vendor.
- Karada.aiYou have an OpenAPI spec and want a hosted MCP server from it without writing one.
- The MCP CensusYou're about to add a third-party MCP server and want a quick go or no-go first.
- MELRAYour agent can change real things through MCP, and you want approvals and no blind retries.
- CATTYou want CI-style tests that check what your MCP server did, not just what the agent said.
- Agentic Resource RegistryYour team keeps rebuilding the same MCP servers and skills, and you want one approved place to install from.
Each listing.
The directory page, alternatives in the same category, and a head-to-head where we have one.
- BifrostAlternatives
- Gauge CLIAlternatives
- PomeradoAlternatives
- NitroStackAlternatives
- Karada.aiAlternatives
- The MCP CensusAlternatives
- MELRAAlternatives
- CATTAlternatives
- Agentic Resource RegistryAlternatives
Category pages list every tool in those categories, including ones left off this page. Built one of these? Get it featured in its category.
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