mailbox
warningsmailbox.bot
Physical mail API for AI agents. Send letters, certified mail. Sandbox + live keys via MCP.
https://mailbox.bot/api/mcpWebsiteOAuthMCP 2025-11-25v1.0.1last checked 8 Oct 2026spoke MCP on 100% of 90 checks (30 days)initialize in 528 msWill my client connect?
Decided from what the probe found at the endpoint, and from what each client's own documentation says it can complete. Every row carries the day that documentation was read.
✕Claude CodeNot supported
The authorization server advertises no S256 challenge method, which MCP's authorization spec requires — no compliant client has a method in common with it.
Claude Code docs · read on 2026-08-30
✕Claude (claude.ai & Desktop)Not supported
The authorization server advertises no S256 challenge method, which MCP's authorization spec requires — no compliant client has a method in common with it.
Claude (claude.ai & Desktop) docs · read on 2026-08-30
✕ChatGPTNot supported
The authorization server advertises no S256 challenge method, which MCP's authorization spec requires — no compliant client has a method in common with it.
ChatGPT docs · read on 2026-08-30
✕CursorNot supported
The authorization server advertises no S256 challenge method, which MCP's authorization spec requires — no compliant client has a method in common with it.
Cursor docs · read on 2026-08-30
✕VS Code (Copilot)Not supported
The authorization server advertises no S256 challenge method, which MCP's authorization spec requires — no compliant client has a method in common with it.
VS Code (Copilot) docs · read on 2026-08-30
How to authenticate
Checked against the endpoint by our probe on 8 Oct 2026. These are the capabilities the server advertises, not a prediction about any particular client.
| Scheme | OAuth |
|---|---|
| Issuer | https://mailbox.bot |
| Dynamic client registration | ✕Not advertised A client that cannot register itself needs credentials issued out of band before it can begin the flow. |
| Client ID Metadata Document | ✕Not advertised |
| PKCE | ✕None advertised MCP requires S256; a client that implements only that has no method in common with this server. |
| Scopes | agent.inbox.read, agent.inbox.report, agent.inbox.propose, agent.read, agent.write, mailbox.read, mailbox.write, inbound.item.read, inbound.item.action, inbound.item.scan.read, inbound.read, message.send, webhook.read, webhook.manage, billing.read, mail.send, document.read |
| Protected-resource metadata | ✓Published (RFC 9728) |
| Anonymous access | Handshake succeeds; 45 tools listable |
| Credentials demanded in prose | ✕send_outbound_mail, list_agent_inbox, get_agent_inbox_context, get_agent_inbox_sources, list_agent_inbox_scans, get_agent_inbox_scan, get_agent_inbox_activity, report_agent_inbox_outcome, get_agent_inbox_handling, propose_agent_inbox_handling, seed_agent_inbox_sandbox, create_webhook_endpoint, list_inbound_items, get_inbound_item_sources These tools are listed anonymously and their own descriptions ask for an account or key, but no challenge is issued — so a client has nothing to act on and the refusal arrives as a tool error. |
What the probe found
14 of the 45 tools listed anonymously say in their own descriptions that they need an account or a key (send_outbound_mail, list_agent_inbox, get_agent_inbox_context, get_agent_inbox_sources, list_agent_inbox_scans, get_agent_inbox_scan, get_agent_inbox_activity, report_agent_inbox_outcome, get_agent_inbox_handling, propose_agent_inbox_handling, seed_agent_inbox_sandbox, create_webhook_endpoint, list_inbound_items, get_inbound_item_sources), but the endpoint issued no WWW-Authenticate challenge. The requirement is stated only in prose, so a call reaches the tool and comes back as a tool error instead of an authorization step.
A cross-origin preflight came back without Access-Control-Allow-Origin, so the endpoint is reachable from native clients only — code running in a web page is stopped by the browser before a request is ever sent.
The server exposes a public surface before authorization: get_mailbox, get_usage, list_inbound_forwarding_addresses, list_inbound_mail, get_inbound_mail, list_postal_threads, get_postal_thread, get_mailbox_md, propose_mailbox_md_edit, send_facility_message, list_facility_conversations, get_facility_messages, update_webhook, send_outbound_mail, list_outbound_mail, get_outbound_mail, cancel_outbound_mail, create_test_outbound_mail, advance_test_outbound_mail, list_agent_inbox, get_agent_inbox_context, get_agent_inbox_sources, list_agent_inbox_scans, get_agent_inbox_scan, get_agent_inbox_activity, report_agent_inbox_outcome, get_agent_inbox_handling, propose_agent_inbox_handling, seed_agent_inbox_sandbox, list_webhook_endpoints, create_webhook_endpoint, update_webhook_endpoint, test_webhook_endpoint, test_webhook_endpoint_with_sample, rotate_webhook_endpoint_secret, list_webhook_deliveries, replay_webhook_delivery, list_inbound_items, get_inbound_item_sources, search_inbound_items, get_inbound_item, get_inbound_pages, quote_inbound_forward, request_inbound_action, get_inbound_activity.
Tools
Contract history
Instructions rewritten: get_inbound_activity, get_inbound_item, get_inbound_pages, get_mailbox, list_inbound_items, quote_inbound_forward, request_inbound_action, search_inbound_items. The description an agent follows changed; the callable contract may not have.
Instructions rewritten: get_inbound_item, get_inbound_pages. The description an agent follows changed; the callable contract may not have.
Instructions rewritten: get_agent_inbox_scan, get_inbound_item, list_agent_inbox, list_agent_inbox_scans, request_inbound_action. The description an agent follows changed; the callable contract may not have.
Breaking: create_webhook_endpoint, list_webhook_deliveries, list_webhook_endpoints, rotate_webhook_endpoint_secret, update_webhook_endpoint, verify_webhook_endpoint
Instructions rewritten: create_webhook_endpoint, list_webhook_deliveries, list_webhook_endpoints, replay_webhook_delivery, rotate_webhook_endpoint_secret, test_webhook_endpoint, update_webhook_endpoint. The description an agent follows changed; the callable contract may not have.
Breaking: get_inbound_item, request_inbound_action
Instructions rewritten: get_agent_inbox_activity, get_agent_inbox_context, get_agent_inbox_handling, get_agent_inbox_scan, get_agent_inbox_sources, get_inbound_item_sources, list_agent_inbox, list_agent_inbox_scans, propose_agent_inbox_handling, report_agent_inbox_outcome, seed_agent_inbox_sandbox. The description an agent follows changed; the callable contract may not have.
Instructions rewritten: get_agent_inbox_sources, get_inbound_item_sources, list_agent_inbox, list_inbound_items. The description an agent follows changed; the callable contract may not have.
Instructions rewritten: get_agent_inbox_context, list_agent_inbox. The description an agent follows changed; the callable contract may not have.
Breaking: get_agent_inbox_context
Instructions rewritten: get_facility_messages, list_facility_conversations, send_facility_message. The description an agent follows changed; the callable contract may not have.
Instructions rewritten: create_test_outbound_mail, send_outbound_mail. The description an agent follows changed; the callable contract may not have.
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Status for a README, from the last probe — cached an hour, so up to seven hours behind the endpoint. Links back to this page.
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