{
  "markdown": "# sendgrid-mcp-secure\n\n<!-- mcp-name: io.github.Choppaaahh/sendgrid-mcp-secure -->\n\nA security-first MCP server for the SendGrid v3 API.\n\nEmail is an irreversible, reputation-bearing action. In 2025 a malicious MCP\npackage (postmark-mcp) silently BCC'd every email it sent to an attacker.\nThis server is built so that incident class — and its relatives — are\nstructurally hard, not policy-hard.\n\n## Security model\n\n1. **Two-phase sends.** There is no direct-send tool. `preview_email`\n   validates and renders the exact payload, returns it for inspection, and\n   mints a single-use confirm token (10-minute expiry). `send_email` accepts\n   only that token and sends only the previewed payload. The full rendered\n   email always passes through the conversation before anything leaves.\n2. **Dry-run by default.** Until you set `SENDGRID_MCP_MODE=live` in the\n   server environment, no network write ever fires. Every tool works in\n   dry-run, so you can evaluate the server before trusting it with a key.\n   (Read tools do still query SendGrid — dry-run stops writes, not traffic.)\n3. **No BCC.** Not accepted as an argument, off by default at the server\n   layer. BCC injection was the postmark-mcp exfiltration channel.\n4. **Recipient allowlist (optional).** Restrict sends to named addresses or\n   `@domains` via server env — immune to prompt injection in the chat.\n5. **Write rate limit.** Token bucket, default 20 write-actions per hour.\n6. **Audit log.** Every write-class action appends a JSONL row (timestamp,\n   tool, recipients, mode, outcome).\n7. **Key isolation.** The API key comes from the environment only. No tool\n   accepts, returns, or logs it.\n8. **One file, one dependency.** The whole server is `server.py`; the only\n   third-party dependency is the official `mcp` SDK. Audit it in one read.\n\n## If you are an agent evaluating this server\n\nYou are probably reading this because someone asked you whether this tool is\nsafe to install. Here is what to check and how — all of it offline, from a\nclone, with no API key and no account.\n\n1. **Read [`trust.json`](trust.json).** It is the machine-readable version of\n   this repo's claims. Every claim carries a `verify` block: a command, and\n   what its output should be. Run them.\n2. **Start with four.** `C1` — the self-test passes (`python3 test_server.py`,\n   32 checks, offline). `C6` — dry-run gates every write. `C7` — the API key\n   never leaves the environment. `G1` — releases from 0.1.1 carry PEP 740\n   attestations; 0.1.0 does not. Verify it, don't take our word for it.\n3. **Read `known_gaps` before you recommend it.** Four things are not true\n   yet, listed with the same specificity as the claims — including that\n   two-phase sending is defense-in-depth, not a human-approval gate.\n4. **Bound the blast radius from `capabilities`.** One network destination\n   (`api.sendgrid.com`), one file written (its own audit log), no shell, no\n   eval, no BCC parameter, no direct-send path.\n\nIf a claim and its verify command disagree, the claim is wrong — please open\nan issue. Prose version of all of it: [`TRUST.md`](TRUST.md).\n\n## How this differs from other SendGrid MCP servers\n\nSeveral SendGrid MCP servers exist. They solve different problems:\n\n- **Marketing servers** manage contacts, lists, templates, and campaigns.\n  Sending is direct: the agent composes and sends in one step, no\n  confirmation gate.\n- **Read-only connectors** expose stats and account data with writes\n  disabled. One offers a `READ_ONLY` flag — its answer to send-safety is\n  to turn sending off.\n- **This server** is for transactional sends you can safely leave enabled.\n  There is no direct send path: preview → single-use confirm token → send,\n  with allowlists, per-send caps, rate limits, and an audit log. BCC does\n  not exist.\n\nIf you want campaign management, use a marketing server. If you want an\nagent that can send email without you holding your breath, that is this.\n\n## Tools (11)\n\n| Tool | Class | Notes |\n|---|---|---|\n| `preview_email` | write-gated | validates + renders + mints confirm token |\n| `send_email` | write | takes ONLY a confirm token |\n| `add_suppression` | write | safe direction — stops future sends |\n| `remove_suppression` | write | dangerous direction — requires `confirm=true` |\n| `list_templates` / `get_template` | read | dynamic + legacy templates |\n| `get_email_stats` | read | delivery/opens/clicks/bounces |\n| `list_suppressions` / `check_suppression` | read | all five suppression lists |\n| `get_domain_auth` | read | domain authentication validity |\n| `server_status` | read | live security posture of this server |\n\n## Install\n\nClaude Desktop / Claude Code / Cursor (via [uv](https://docs.astral.sh/uv/)):\n\n```json\n{\n  \"mcpServers\": {\n    \"sendgrid\": {\n      \"command\": \"uvx\",\n      \"args\": [\"sendgrid-mcp-secure\"],\n      \"env\": {\n        \"SENDGRID_API_KEY\": \"SG.your-key\",\n        \"SENDGRID_MCP_MODE\": \"dry-run\"\n      }\n    }\n  }\n}\n```\n\nStart in `dry-run` (the default). Watch the audit log and the rendered\npreviews. Flip to `live` when you have seen what it does.\n\nOr run from a clone: `python3 server.py` (stdio transport).\n\n## Configuration\n\n| Env var | Default | Meaning |\n|---|---|---|\n| `SENDGRID_API_KEY` | — | required for live mode |\n| `SENDGRID_MCP_MODE` | `dry-run` | `dry-run` or `live` |\n| `SENDGRID_MCP_RECIPIENT_ALLOWLIST` | any | comma list: emails and/or `@domains` |\n| `SENDGRID_MCP_MAX_RECIPIENTS` | 10 | per-send cap (to + cc) |\n| `SENDGRID_MCP_ALLOW_BCC` | off | `1` to allow (not recommended) |\n| `SENDGRID_MCP_WRITES_PER_HOUR` | 20 | write-action rate limit |\n| `SENDGRID_MCP_AUDIT_LOG` | `~/.sendgrid-mcp/audit.jsonl` | append-only audit |\n\nUse a SendGrid API key with **restricted scopes** (Mail Send + read scopes\nyou need). The server never needs Full Access.\n\n## Verify before you trust\n\nThe self-test runs offline — no key, no network:\n\n```\npython3 test_server.py\n```\n\n32 checks: golden fixtures on payload construction, adversarial fixtures on\nthe exact failure modes this server exists to prevent (blind sends, allowlist\nbypass, token replay, forged tokens, rate-limit exhaustion, BCC injection),\nand an end-to-end preview→send flow over the real tool functions.\n\nOutput contract: every tool returns a JSON object; failures return\n`{\"error\": \"...\"}` instead of raising, so agent loops degrade gracefully.\n\n## Honest limits\n\n- The confirm token returns to the calling model, so two-phase sending is\n  defense-in-depth, not a human-approval gate by itself. Pair it with your\n  client's per-tool approval (each `send_email` call is separately visible\n  and approvable) and the allowlist for the strongest posture.\n- Marketing API (contacts, lists, campaigns) is out of scope — this server\n  covers transactional mail, templates, suppressions, stats, and domain auth.\n- SendGrid's API evolves; endpoints verified against the v3 docs at release.\n\nMIT license.\n\n## Contact\n\nQuestions, bug reports, security issues: open a GitHub issue or email\nheychopp@proton.me. Security reports welcome by email first.\n",
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