API · Manage · Signing
Complete signing session.
Records a signer's completed signature for one envelope slot and writes the ESIGN/UETA evidence row (EsraAcknowledgement): the exact attestation text the signer accepted, a salted hash of the source IP, and the completion timestamp.
Signature-record association: the caller MUST present the single-use session token (minted when the envelope was sent) in the X-Signing-Session-Token header. Org bearer auth alone returns 403 invalid_session_token — possession of the org key does not let one principal complete another signer's slot.
Document linkage cascade: - first completed signer transitions every envelope document sent → partially_signed; - the final signer completes the envelope, transitions documents to executed (status signed), merges the signature evidence summary into the document payload, refreshes the executed artifact (signature blocks render /s/ <name>), and freezes a new DocumentVersion pinning the executed body hash; - document.executed is emitted on the entity's webhook stream.
In test and sandbox modes an agent holding the session token may complete the session under the agent_authorized method. In live mode, roles whose template signer spec forbids agent_authorized require the human-OAuth signing-session flow (POST /signing_sessions).
Last updated
Header Parameters
X-Signing-Session-TokenstringRequiredSingle-use session token minted at send time; never logged.
Request Body
application/json
TypeScript Definitions
Use the request body type in TypeScript.
electronic_signature_textstringRequiredExact attestation text the signer accepted; persisted verbatim on the evidence row.
signature_blobstringOptionalOptional drawn/typed signature image payload (data URI).
client_metadataobjectOptionalResponse Body
application/json
application/problem+json
application/problem+json
application/problem+json
Request
curl -X POST "https://api.mattermode.com/v1/signing_sessions/{id}/complete" \ -H "X-Signing-Session-Token: string" \ -H "Content-Type: application/json" \ -d '{ "electronic_signature_text": "string" }'const body = JSON.stringify({ "electronic_signature_text": "string"})fetch("https://api.mattermode.com/v1/signing_sessions/{id}/complete", { method: "POST", headers: { "Content-Type": "application/json", "X-Signing-Session-Token": "string" }, body})package mainimport ( "fmt" "net/http" "io/ioutil" "strings")func main() { url := "https://api.mattermode.com/v1/signing_sessions/{id}/complete" body := strings.NewReader(`{ "electronic_signature_text": "string" }`) req, _ := http.NewRequest("POST", url, body) req.Header.Add("X-Signing-Session-Token", "string") req.Header.Add("Content-Type", "application/json") res, _ := http.DefaultClient.Do(req) defer res.Body.Close() body, _ := ioutil.ReadAll(res.Body) fmt.Println(res) fmt.Println(string(body))}import requestsheaders = { "Authorization": "Bearer sk_test_4eC39HqLyjWDarjtT1zdp7dc", "Matter-Version": "2026-06-10", "Idempotency-Key": "ee7c3a9b-3f1a-4d8e-9b2a-7c5e1f0a2d4b",}payload = { "electronic_signature_text": "example"}resp = requests.post( "https://api.mattermode.com/v1/signing_sessions/id_placeholder/complete", headers=headers, json=payload,)resp.raise_for_status()print(resp.json())import java.net.URI;import java.net.http.HttpClient;import java.net.http.HttpRequest;import java.net.http.HttpResponse;import java.net.http.HttpResponse.BodyHandlers;import java.time.Duration;import java.net.http.HttpRequest.BodyPublishers;var body = BodyPublishers.ofString("""{ "electronic_signature_text": "string"}""");HttpClient client = HttpClient.newBuilder() .connectTimeout(Duration.ofSeconds(10)) .build();HttpRequest.Builder requestBuilder = HttpRequest.newBuilder() .uri(URI.create("https://api.mattermode.com/v1/signing_sessions/{id}/complete")) .header("X-Signing-Session-Token", "string") .header("Content-Type", "application/json") .POST(body) .build();try { HttpResponse<String> response = client.send(requestBuilder.build(), BodyHandlers.ofString()); System.out.println("Status code: " + response.statusCode()); System.out.println("Response body: " + response.body());} catch (Exception e) { e.printStackTrace();}using System;using System.Net.Http;using System.Text;var body = new StringContent("""{ "electronic_signature_text": "string"}""", Encoding.UTF8, "application/json");var client = new HttpClient();client.DefaultRequestHeaders.Add("X-Signing-Session-Token", "string");var response = await client.PostAsync("https://api.mattermode.com/v1/signing_sessions/{id}/complete", body);var responseBody = await response.Content.ReadAsStringAsync();curl --request POST 'https://api.mattermode.com/v1/signing_sessions/id_placeholder/complete' \ --header 'Authorization: Bearer sk_test_4eC39HqLyjWDarjtT1zdp7dc' \ --header 'Matter-Version: 2026-06-10' \ --header 'Idempotency-Key: ee7c3a9b-3f1a-4d8e-9b2a-7c5e1f0a2d4b' \ --header 'Content-Type: application/json' \ --data '{ "electronic_signature_text": "example"}'const response = await fetch("https://api.mattermode.com/v1/signing_sessions/id_placeholder/complete", { method: "POST", headers: { "Authorization": "Bearer sk_test_4eC39HqLyjWDarjtT1zdp7dc", "Matter-Version": "2026-06-10", "Idempotency-Key": "ee7c3a9b-3f1a-4d8e-9b2a-7c5e1f0a2d4b", "Content-Type": "application/json", }, body: JSON.stringify({ "electronic_signature_text": "example" }),});if (!response.ok) { throw new Error(`Matter API ${response.status}: ${await response.text()}`);}const data = await response.json();console.log(data);Response
application/json{
"session": {
"id": "string",
"object": "signing_session",
"target": {
"document_id": "string",
"signing_envelope_id": "string",
"signer_id": "string"
},
"stakeholder_id": "string",
"human_clerk_user_id": "string",
"created_at": 0,
"expires_at": 0,
"status": "pending",
"signature_token": "string",
"disclosure_packet_hash": "string",
"livemode": true
},
"acknowledgement": {},
"envelope_status": "draft",
"document_ids": [
"string"
]
}{
"type": "https://mattermode.com/docs/errors/invalid_state_transition",
"title": "Invalid state transition",
"status": 409,
"detail": "Entity ent_Nq3KcAbc is in state `dissolved` and cannot be dissolved again.",
"instance": "/requests/req_Qw9xYz8A",
"code": "invalid_state_transition",
"param": "founders[0].equity",
"doc_url": "https://mattermode.com/docs/guides/errors#invalid_state_transition",
"request_id": "req_Qw9xYz8A",
"retry_after": 30,
"authorized_by": {
"human_principal_id": "usr_4Kj2m8pQ",
"agent_id": "agt_Nq3KcAbc"
}
}{
"type": "https://mattermode.com/docs/errors/invalid_state_transition",
"title": "Invalid state transition",
"status": 409,
"detail": "Entity ent_Nq3KcAbc is in state `dissolved` and cannot be dissolved again.",
"instance": "/requests/req_Qw9xYz8A",
"code": "invalid_state_transition",
"param": "founders[0].equity",
"doc_url": "https://mattermode.com/docs/guides/errors#invalid_state_transition",
"request_id": "req_Qw9xYz8A",
"retry_after": 30,
"authorized_by": {
"human_principal_id": "usr_4Kj2m8pQ",
"agent_id": "agt_Nq3KcAbc"
}
}{
"type": "https://mattermode.com/docs/errors/invalid_state_transition",
"title": "Invalid state transition",
"status": 409,
"detail": "Entity ent_Nq3KcAbc is in state `dissolved` and cannot be dissolved again.",
"instance": "/requests/req_Qw9xYz8A",
"code": "invalid_state_transition",
"param": "founders[0].equity",
"doc_url": "https://mattermode.com/docs/guides/errors#invalid_state_transition",
"request_id": "req_Qw9xYz8A",
"retry_after": 30,
"authorized_by": {
"human_principal_id": "usr_4Kj2m8pQ",
"agent_id": "agt_Nq3KcAbc"
}
}