# Glass protocol
Glass uses MCP JSON-RPC for transport. It uses a versioned Glass envelope for
operation semantics.
The envelope is defined by
[glass-protocol-v1.schema.json](schema/glass-protocol-v1.schema.json) and the
Rust `glass::protocol` module.
## MCP mapping
| JSON-RPC `id` | `requestId` |
| `params.name` | `operation` with the `browser.` prefix |
| `params.arguments` | `payload` |
| Daemon session and lease context | `sessionId` and `mutationLease` |
The CLI and SDKs use the same operation names and payload fields. MCP keeps
JSON-RPC success and error framing. The operation payload remains bounded and
versioned.
A request must contain protocol version `1`, a non-empty operation name, and a
bounded request ID. A response contains one result or one structured error.
The checked-in [protocol golden fixture](../tests/fixtures/protocol-golden-v1.json)
covers read, leased mutation, workflow, success, and typed-error envelopes.
Rust tests round-trip the fixture. MCP tests check the canonical mapping.
## Compatibility
Glass rejects unknown envelope fields. Additive fields must be optional. A
change to a required field or validation meaning requires a new schema version
and a migration note.
Protocol deadlines are limited to fifteen minutes. Each transport keeps its
own frame limits.