Short answer
MCP, the Model Context Protocol, is the established open standard for runtime access to tools, resources, and prompts. UHP, the Unified Harness Protocol, standardizes the configured-harness boundary: harness discovery, model selection, skills, attached MCP servers, tool restrictions, Full-class lifecycle management, tasks, sessions, streaming, files, and cancellation. UHP does not replace MCP. A common architecture configures MCP servers on the harness through UHP, then uses MCP to call tools exposed by those servers at runtime; harness-native tools may use the runtime's own mechanism. UHP is a newer open standard with a versioned specification dated 2026-08-11, a reference implementation, a conformance suite, and one independent client implementation.
- MCP standardizes runtime capability access; UHP standardizes how a harness is configured, selected, and driven. Different responsibilities, used together rather than chosen between.
- MCP is an established, widely adopted open standard, now hosted by the Agentic AI Foundation under the Linux Foundation. UHP is a newer open standard for the configured-harness boundary, with a versioned specification, reference implementation, conformance suite, and one independent client implementation.
- Neither replaces the other. At Full conformance a product attaches MCP servers by configuring the harness's mcpServers field through UHP, while MCP remains the runtime wire when that harness calls tools exposed by those servers. Facts verified 2026-08-27.
Two open standards, two layers
The agent stack has more than one boundary, and MCP and UHP define different responsibilities. MCP, introduced by Anthropic in 2024 and donated in 2025 to the Agentic AI Foundation under the Linux Foundation, is an open standard for runtime access to tools, resources, and prompts through a host, client, and server model. UHP, the Unified Harness Protocol, is an open standard for the configured-harness boundary: how a product discovers, configures, selects, and drives a harness, including its model, skills, MCP server attachments, tool restrictions, tasks, sessions, streaming, files, and cancellation. MCP carries calls to tools exposed by configured MCP servers; UHP governs the harness configuration and the product-facing task lifecycle. UHP is newer than MCP, with a versioned specification, reference implementation, conformance suite, and one independent client implementation. All facts here are from public materials, verified 2026-08-27.
The questions each open standard answers
These are not competing answers to one question; they are answers to different questions at different layers.
- What it connects
- MCP connects an MCP client to servers exposing tools, resources, and prompts. UHP connects a product to a harness through one unified interface: with the same contract, the product selects a harness, configures what it is made of (its model, skills, and MCP servers, and which tools are available), and drives it.
- Where it operates
- MCP operates at runtime between MCP clients and servers. UHP is one client-server interface for selecting and driving a harness, and for setting up what the harness is made of: its model, skills, MCP servers, and which tools are available.
- What it carries
- MCP carries runtime messages for tools, resources, and prompts. UHP carries harness configurations and lifecycle operations, plus tasks, sessions, streaming, files, cancellation, and results.
MCP and UHP, boundary by boundary
This maps each open standard's boundary and scope; it is not a feature or maturity scorecard. Facts as of 2026-08-27.
| Dimension | MCP | UHP |
|---|---|---|
| Primary boundary | Agent to tools, resources, and prompts | Product to a configured harness, including harness configuration and driving |
| Where it sits | Inside an AI application or agent harness, client to servers | One client-server interface: a product selects and drives a harness through a UHP server, and sets up what the harness is made of: its model, skills, MCP servers, and which tools are available |
| What it carries | Tool, resource, and prompt messages and capabilities | Harness configuration objects and lifecycle operations; tasks, responses, streamed events, sessions, files, and cancellation |
| Maturity and governance | Established and widely adopted; hosted by the Agentic AI Foundation under the Linux Foundation | Newer open standard; versioned spec, reference implementation, conformance suite, and one independent client implementation |
| How they compose | Carries runtime calls to tools exposed by configured MCP servers; harness-native tools use the runtime's own mechanism, while UHP stays in use for streaming, sessions, files, and cancellation during the run | Lets a product set the harness's model, skills, MCP servers, and available tools, then drive the harness through the server |
When each open standard is the one you reach for
- You are giving an agent tools and data sources
- That is MCP's layer: the established open standard for runtime access to tools, resources, and prompts. At Full conformance, a product uses UHP harness endpoints to configure which MCP servers are attached through the harness's mcpServers field, while MCP carries the runtime tool calls to those servers.
- You are invoking a harness from an application
- That is UHP's layer: configuring the harness (model, skills, MCP servers, tool restrictions), then driving it through tasks, sessions, streaming, files, and cancellation, as an open standard with a versioned specification.
- You are building a product that runs agents and calls tools
- UHP is the open standard for the layer your product builds on: through UHP, your product sets up the harness that runs the agent, selects it, and drives it. MCP then carries runtime calls to tools exposed by the configured MCP servers, while harness-native tools may use the runtime's own mechanism.
FAQ
- Is UHP a competitor to MCP?
- No. MCP standardizes runtime access to tools and data; UHP standardizes how a product sets up, selects, and drives a harness. They compose: through UHP a product adds MCP servers to the harness, and MCP carries runtime calls to tools exposed by those servers.
- Does UHP replace MCP?
- No. UHP does not define MCP tool discovery or tool-call messages and is not a substitute for MCP. It standardizes which MCP servers, skills, model, and tool restrictions are configured on a harness and how a product drives it. At runtime, MCP remains the wire for tools exposed by those MCP servers; harness-native tools may use the runtime's own mechanism.
- Is UHP an open standard?
- Yes. The Unified Harness Protocol is an open standard. As of 2026-08-27, its public materials include a versioned specification dated 2026-08-11, a reference implementation, and a conformance suite, and the independent adoption tracker lists one independent client implementation, SuperQode. It is newer than MCP and covers a different layer of the agent stack.