---
title: "Changes to Attach to an existing tool router session (v3.1)"
method: POST
path: "/api/v3.1/tool_router/session/{session_id}/attach"
---

# Changes to Attach to an existing tool router session (v3.1)

`POST /api/v3.1/tool_router/session/{session_id}/attach`

> Every recorded change to this endpoint, newest first.

## Timeline

Changed in 5 of 61 revisions.

- **2026-07-15** `5c81af384429` — 1 info
- **2026-06-17** `589a7d115a5e` — 2 info
- **2026-05-06** `6ccbbc3d49b9` — 1 breaking, 3 info
- **2026-05-05** `5a3709be76a7` — 1 breaking, 2 info
- **2026-05-05** `52c71f747c65` — 1 info

## Changes

- **2026-07-15** `5c81af384429` — 1 info
  - removed the non-success response with the status `403`
- **2026-06-17** `589a7d115a5e` — 2 info
  - the endpoint scheme security `CookieAuth` was removed from the API
  - the endpoint scheme security `UserApiKeyAuth` was removed from the API
- **2026-05-06** `6ccbbc3d49b9` — 1 breaking, 3 info
  - the `config/connected_accounts/additionalProperties/` response's property type changed from `string` to `array`, and format from `connectedAccountId` to no format for status `200`
  - added the new optional request property `experimental/custom_toolkits/items/preload`
  - added the new optional request property `experimental/custom_toolkits/items/tools/items/preload`
  - added the new optional request property `experimental/custom_tools/items/preload`
- **2026-05-05** `5a3709be76a7` — 1 breaking, 2 info
  - response property `config/preload/tools` list-of-types was widened by adding types `string` to media type `application/json` of response `200`
  - added the required property `config/execute` to the response with the `200` status
  - added the required property `config/search` to the response with the `200` status
- **2026-05-05** `52c71f747c65` — 1 info
  - endpoint added

---

[Operation](https://skmtc.dev/composiohq/apis/composio-platform-api-v3-1/docs/api/v3.1/tool_router/session/:session_id/attach/post.md) · [API](https://skmtc.dev/composiohq/apis/composio-platform-api-v3-1.md) · [Page](https://skmtc.dev/composiohq/apis/composio-platform-api-v3-1/changes/api/v3.1/tool_router/session/:session_id/attach/post)