MCP client bridge plugin: connects to external Model Context Protocol servers and registers their tools on ctx.tools, making them available to the model as native tools under server-qualified names (mcp__<serverName>__<rawName>).

Usage

One plugin instance per MCP server in cordis.yml:

- id: mcp-github
  name: '@deepseek-ai/dsh-mcp-client'
  config:
    serverName: github
    transport: stdio
    command: npx
    args: ['-y', '@modelcontextprotocol/server-github']
    env:
      GITHUB_TOKEN: !!js process.env.GITHUB_TOKEN

- id: mcp-web
  name: '@deepseek-ai/dsh-mcp-client'
  config:
    serverName: web
    transport: streamable-http
    url: http://localhost:3000/mcp
    headers:
      Authorization: !!js '`Bearer ${process.env.MCP_TOKEN}`'

The model sees mcp__github__create_issue, mcp__web__search, … — the same server-qualified shape Claude Code and Codex use. HMR hot-swaps: editing the entry triggers disconnect + reconnect without process restart; an unchanged serverName reproduces identical tool names.

Config

Field	Transport	Required	Description
`transport`	both	yes	`"stdio"` or `"streamable-http"`
`serverName`	both	yes	Namespace for this server's model-facing tool names; `[A-Za-z0-9_-]{1,32}`, unique across live instances
`command`	stdio	yes	Executable to spawn
`args`	stdio	no	Arguments passed to the command
`env`	stdio	no	Extra env vars merged on top of scrubbed ambient env
`cwd`	stdio	no	Working directory for the child process
`url`	http	yes	MCP server URL
`headers`	http	no	Extra headers (e.g. auth tokens)
`toolCallTimeoutMs`	both	no	Timeout per `callTool` invocation (default 60000)

Tool naming

Every MCP tool has two names: the raw MCP name (sent on the wire in tools/call) and the public name mcp__<serverName>__<rawName> registered on ctx.tools. Public names are normalized to the DeepSeek function-name contract (64 chars, [A-Za-z0-9_-]); when replacement or truncation changes the name, a deterministic 12-hex-char hash of (serverName, rawName) is appended so distinct tools never collapse into one name. Names are pure functions of (serverName, rawName) — connection order, re-syncs, and other servers never rename a tool.

Two servers publishing the same raw name (e.g. search) coexist under their namespaces.
A duplicate serverName across live instances fails the later plugin instance at load.
A server listing the same tool name twice is rejected as an invalid tool list.
A foreign registration squatting on this server's namespace rolls back the whole generation (never a partial set), with a loud error.

Behavior

On connect: listTools() → registers each tool via ctx.tools.register() under its public name.
Listens for notifications/tools/list_changed → re-syncs; a failed re-sync keeps the previous generation registered.
Tool execute: client.callTool({ name: rawName, arguments }, { signal }) with timeout + abort support — the public name is never sent to the server.
Image content in results is discarded with a placeholder (the harness has no image block type).
On disconnect/crash: all tools are unregistered; no auto-reconnect.

Services consumed

Service	Usage
`ctx.tools`	Register/unregister MCP tools

Model Experience

Discovered MCP tools

What the model sees: After initial discovery succeeds, each advertised MCP tool appears as a native tool named mcp__<serverName>__<rawName> (or its deterministic normalized form), with the server-provided description and input schema. A successful re-sync replaces the generation; plugin disposal removes it.

Token effect: Data-dependent schema cost is paid on every request while the tools are registered. Re-sync replaces rather than accumulates schemas, and the server-qualified name adds tokens to every tool definition and call.

Tool-call history and results

What the model sees: The public tool name and JSON arguments remain in assistant history. Text result blocks are joined with newlines into one retained text result; image, audio, resource, and unsupported blocks become short placeholders, and MCP isError results follow the registry's model-visible error path.

Token effect: Arguments and mapped text are retained until compaction. Binary and resource payloads are discarded rather than added to context.

Known Limitations and Deferred Work

Initial discovery is asynchronous — plugin load does not wait for connection and listTools(), so a turn started immediately after boot or HMR can assemble before the MCP tools are registered.
Tools are the only bridged MCP capability — Resources and Prompts have no harness consumption surface and are deferred.
Crash recovery is manual — transport closure unregisters the server's tools, but reconnect requires an HMR reload or harness restart.
Non-text results are lossy — image, audio, and resource payloads are replaced with placeholders, and a structured-only result has no model-visible structured representation.