{"uid":"cap_0i6Rthr8GTEbFUP_L_CV4","slug":"agentmail-reply-4671f3f6","name":"AgentMail Reply To Message","description":"Reply To Message","url":"https://mpp.api.agentmail.to/v0/inboxes/:inbox_id/messages/:message_id/reply?utm_source=zero.xyz","method":"POST","headers":{},"bodySchema":{"type":"object","title":"ReplyToMessageRequest","properties":{"cc":{"oneOf":[{"type":"string"},{"type":"array","items":{"type":"string"}}],"title":"Addresses"},"to":{"oneOf":[{"type":"string"},{"type":"array","items":{"type":"string"}}],"title":"Addresses"},"bcc":{"oneOf":[{"type":"string"},{"type":"array","items":{"type":"string"}}],"title":"Addresses"},"html":{"type":"string","title":"MessageHtml","description":"HTML body of message."},"text":{"type":"string","title":"MessageText","description":"Plain text body of message."},"labels":{"type":"array","items":{"type":"string"},"title":"MessageLabels","description":"Labels of message."},"headers":{"type":"object","title":"SendMessageHeaders","description":"Headers to include in message.","additionalProperties":{"type":"string"}},"reply_to":{"oneOf":[{"type":"string"},{"type":"array","items":{"type":"string"}}],"title":"Addresses"},"reply_all":{"type":"boolean","title":"ReplyAll","description":"Reply to all recipients of the original message."},"attachments":{"type":"array","items":{"type":"object","title":"SendAttachment","properties":{"url":{"type":"string","description":"URL to the attachment."},"content":{"type":"string","description":"Base64 encoded content of attachment."},"filename":{"type":"string","title":"AttachmentFilename","description":"Filename of attachment."},"content_id":{"type":"string","title":"AttachmentContentId","description":"Content ID of attachment."},"content_type":{"type":"string","title":"AttachmentContentType","description":"Content type of attachment."},"content_disposition":{"enum":["inline","attachment"],"type":"string","title":"AttachmentContentDisposition","description":"Content disposition of attachment."}}},"title":"SendMessageAttachments","description":"Attachments to include in message."}}},"responseSchema":{"type":"object","title":"SendMessageResponse","required":["message_id","thread_id"],"properties":{"thread_id":{"type":"string","title":"ThreadId","description":"ID of thread."},"message_id":{"type":"string","title":"MessageId","description":"ID of message."}}},"example":null,"exampleRequest":null,"tags":["email","inboxes","domains","drafts","threads","webhooks","messaging","ai","social"],"displayCostAmount":"0.01","displayCostAsset":"USDC","priceDynamic":false,"priceHint":null,"priceStatus":"priced","priceSource":"unknown","requiresHandshake":false,"reviewCount":0,"rating":{"score":"0.00","successRate":"0.00","reviews":0,"stars":null,"state":"unrated"},"availabilityStatus":"unknown","priceObserved":null,"sessionDeposit":null,"pricing":{"kind":"static","summary":"$0.01/call","primary":{"kind":"static","protocol":"mpp","network":"tempo","amountUsd":"0.01","per":"call","confidence":"exact"},"accepted":[{"kind":"static","protocol":"mpp","network":"tempo","amountUsd":"0.01","per":"call","confidence":"exact"}]},"paymentMethods":[{"uid":"pm_9o1PKl6ynd6tYZaHoHk39","protocol":"mpp","methodType":"crypto","chain":"tempo","mode":"charge","costAmount":"0.01","costPer":"request","priority":0,"asset":null,"unit":"request","depositMicros":null,"planRef":null}],"brandName":"AgentMail","brandSlug":"agentmail","brandBaseUrl":"https://agentmail.to","brandDocsUrl":"https://docs.agentmail.to","whatItDoes":"Sends a reply to a specific email message within an AgentMail inbox, supporting reply-all, CC/BCC, HTML/text bodies, attachments, and custom headers.","exampleAgentPrompt":"Reply to the last email in inbox 'support-agent@agentmail.to' (inbox ID: inbox_abc123, message ID: msg_xyz789) with: 'Thanks for reaching out! We've received your request and will follow up within 24 hours.' — reply all and CC billing@mycompany.com.","exampleUseCases":null,"resultDescription":"Returns a JSON object containing the message_id of the newly sent reply and the thread_id of the email thread it belongs to, confirming the reply was delivered.","failureModes":["Invalid inbox_id or message_id returns 404 Not Found","Missing or invalid Authorization Bearer token returns 401 Unauthorized","Malformed request body (e.g. invalid email address format) returns 400 Bad Request","Inbox not found or inaccessible returns 403 Forbidden","Both html and text body fields absent may result in empty message error","Invalid attachment URL or base64 content may cause attachment delivery failure"],"whenToPreferThis":"Use this endpoint when an AI agent needs to respond to a specific received email message within an AgentMail-managed inbox. Prefer this over sending a new message when the context requires threading (reply-to headers, original message association). Ideal for automated customer support agents, AI email assistants, or any workflow that needs to close the loop on inbound messages.","instructions":null,"reviewSummary":null,"reviewSummaryHighlights":null,"reviewSummaryConcerns":null,"reviewSummaryGeneratedAt":null,"activationCount":0,"lastUsedAt":null,"lastSuccessfullyRanAt":null,"lastHealthCheckAt":"2026-10-12T00:40:34.880Z","isFirstParty":false,"canonicalSlug":"agentmail-reply-4671f3f6"}