# OpenRouter: tool blocks widened to support MCP tool references, VoyageAI provider option

> OpenRouter's Messages API tool blocks (MessagesToolAdditionBlock, MessagesToolRemovalBlock) now accept a union of tool_reference, mcp_tool_reference, and mcp_toolset_reference, with cache_control support added. Existing tool_reference payloads remain valid. The ProviderName enum and ProviderOptions gain new entries including VoyageAI.

| | |
|---|---|
| **Tool** | openrouter |
| **Version** | — |
| **Kind** | announcement |
| **Published** | 2026-07-24 |
| **Observed** | 2026-08-21 |
| **Significance** | 4/5 |
| **Breaking** | yes |
| **Categories** | api-change, breaking |

## What changed


- **MessagesToolAdditionBlock** and **MessagesToolRemovalBlock**: `tool` field widened from a single `tool_reference` object to a union of `tool_reference`, `mcp_tool_reference` (name + server_name), and `mcp_toolset_reference` (server_name). The `type` property moved into the `tool_reference` variant. Existing `{"type": "tool_reference", "name": "..."}` payloads remain valid. `cache_control` property added to both blocks.
- **ProviderName** enum: new value added, affects multiple endpoints
- **ProviderOptions**: new `voyageai` property added across audio, image, and video endpoints
- **AnthropicCompactionBlock**: new `encrypted_content` property
- **ORAnthropicStopReason**: enum value added


## Sources

- [blog_rss](https://openrouter.ai/docs/changelog#july-24-2026) — retrieved 2026-08-21


## Community

_No curated reactions recorded. Facts and community takes are kept in separate layers
and never blended._

---
Canonical: https://changelogs.info/openrouter/openrouter-tool-blocks-widened-to-support-mcp-tool-references-voyageai-provider-
Entity: https://changelogs.info/openrouter
Event ID: `evt_2026-07-24_openrouter_july-24-2026`
Licence: event synthesis © changelogs.info, CC BY 4.0. Linked sources belong to their vendors.