Preface

When integrating MCP tools into DeepSeek Harness (DSH), the larger the tool catalog, the more tool schemas the model sees per turn, increasing both context pressure and API costs. dsh-mcp-lens is a DSH community plugin maintained by labmimors, aiming to handle large-scale MCP tools through two stable model interfaces—mcp_search and mcp_call. It only exposes the exact inputSchema of candidate tools when needed and enforces authorization control over final server/tool calls.

What This Is

dsh-mcp-lens is positioned as a solution to reduce MCP context and API costs. It consolidates a large number of MCP tools into a smaller model-visible surface through two model interfaces, lazy discovery, and precise schema invocation.

Basic information:

  • Repository name: labmimors/dsh-mcp-lens
  • License: MIT
  • GitHub: https://github.com/labmimors/dsh-mcp-lens

Core Features

Two Stable Model Interfaces

The plugin supports searching and invoking 1,000 MCP tools through two model-visible interfaces. The model no longer faces the full tool catalog directly; instead, it completes discovery and invocation through stable interfaces.

Small Candidate Set Exposed Only When Needed

The plugin does not pass all tool schemas to the model. When needed, it exposes the exact inputSchema values for a small ranked set. This reduces the scale of tool definitions the model needs to process per turn.

Calls Controlled by allowTools and denyTools

Final server/tool calls pass through allowTools and denyTools gates. denyTools always takes precedence.

In other words, a remote tool is not exposed to the model unless it matches allowTools; if it also matches denyTools, denyTools takes priority.

Lazy Activation

When lazy activation is enabled, the plugin does not start MCP processes or open MCP sockets. It defers the startup of MCP resources until they are actually needed.

Local Catalog Calculator

The plugin includes a local catalog calculator for self-reporting byte measurements of tool schemas.

Shared results should be treated as self-reported local measurements. They are not signatures and cannot serve as proof that measurement actually occurred.

Dependency-Free GitHub Action Included

The plugin also ships with a dependency-free GitHub Action for auditing checked-in tool payloads. It can push tool payload size checks into CI.

Installation & Enablement

First, ensure the environment meets the following requirements:

  • DeepSeek Harness 0.1.0-rc.6
  • Node.js ^22.19.0 or >=24.0.0
  • pnpm in PATH

The fastest installation method:

dsh plugin --profile web add dsh-mcp-lens@next

The npm next tag currently resolves to 0.1.0-rc.9.

If you need to pin to a reviewed version, you can use:

dsh plugin --profile web add dsh-mcp-lens@0.1.0-rc.9

After installation, you can view the current profile configuration and start Harness:

dsh --profile web --dump-config
dsh --profile web

The first command inspects the current profile configuration, and the second starts the profile.

Typical Usage

After installation, you can prompt Harness as usual without needing to mention mcp_search or mcp_call explicitly in your prompts.

If you use the GitHub Action example from the repository to audit checked-in tool payloads, you can configure it like this:

- uses: labmimors/dsh-mcp-lens@v0.1.0-rc.7
  with:
    tools-file: fixtures/request-header-tools.json

This Action is used to check already-committed tool payloads.

If you integrate an MCP documentation server following the README scenario, no additional API key is needed; however, Harness itself still requires a configured model provider.

Applicable Scenarios & Notes

dsh-mcp-lens is better suited for these scenarios:

  • Tens to thousands of MCP tools
  • Multiple MCP servers
  • Long-tail tool catalogs
  • Carrying all tool schemas in every request creates noticeable context pressure

If you only have a few tools that are used in nearly every request, introducing this plugin may not be necessary.

Before using it, note the following:

  1. The plugin runs with the current dsh process privileges. Before installation, it is recommended to review the source code, the MIT license, the Action version, and the allowTools / denyTools configuration.

  2. denyTools always takes precedence in both search and invocation. If a tool needs to be hidden or disallowed from invocation, denyTools should be used as the priority.

  3. Shared results from the local calculator are only self-reported local measurements—not signatures or proof of measurement.

Conclusion

The value of dsh-mcp-lens lies in consolidating large-scale MCP tool catalogs into two model interfaces, exposing exact inputSchema values when needed, and using allowTools and denyTools to control final invocation. It suits DSH scenarios with a large number of tools, complex catalogs, and a desire to reduce MCP context and API costs.

You can first review the release versions, license, and Action examples in the GitHub repository:

https://github.com/labmimors/dsh-mcp-lens