OpenGrok Go MCP

Useopengrok-go-mcpwhen you want an agent to investigate a large indexed codebase without cloning it locally. It works best for finding symbols, reading files, tracing references, narrowing broad searches, and producing answers with source citations.

It is intentionally honest about OpenGrok's limits. OpenGrok provides full-text search plus ctags definitions, not a full semantic call graph or AST engine. For structural questions, use this server to find the right files and symbols, then verify relationships with language-aware tools when needed.

Required:OPENGROK_MCP_BASE_URL— OpenGrok API base URL ending in/api/v1. On startup the server discovers projects, probes capabilities, and registers only tools that work. A typical reverse-proxied instance needs nothing else.

Copy a block below, replace the URL, restart the client.

{ "mcpServers": { "opengrok": { "command": "/path/to/opengrok-go-mcp", "env": { "OPENGROK_MCP_BASE_URL": "https://your-opengrok-host/source/api/v1" } } } }

Add to~/.claude.jsonundermcpServers, or runclaude mcp add:

go test ./evals/ -count=1 # contract + token benchmark go test ./evals/ -run TestEvalSuite -count=1 # MCP contract only go test ./evals/ -run TestTokenBenchmark -count=1 # token economy only

- Contract eval— hermetic MCP calls against a fake OpenGrok backend; checks outputs, errors, and pagination fields.Δis change vs the committed baseline inevals/baselines/.coverage@Kis the fraction of eval cases exercised.
- Token benchmark— same harness, but measures UTF-8 bytes crossing the MCP wire (tool schemas, requests, responses).Est. tokens= bytes ÷ 4 (rough heuristic, not a specific model tokenizer).
- Surface—full(fine-grained tools),compact(4 consolidated tools, default), orgateway(experimental discover + call).
- ListTools— one-time cost when the client loads the tool list and schemas at session start; usually the largest line item onfull.
- Warm total—ListToolsplus all tool calls in a scenario (request + response bytes). Forgateway,warmexcludes the one-timeopengrok_discovercall;coldincludes it (first session only). Onfullandcompact, cold = warm.
- Min–max— range across the four replay scenarios (symbol lookup, file browse, multi-step symbol search, search-and-read). Per-scenario breakdown is in the collapsed table.
- Δon token rows — change in estimated tokens vs the last committed baseline (evals/baselines/token_report.json).

Last run:2026-06-25· deterministic-replay · est. tokens = bytes÷4 (heuristic, not model-exact)

ListToolsdominates session cost on the full surface (18 tools). Compact (4) and gateway (2) register far fewer schemas.

Warm = ListTools + scenario tool traffic. Gateway warm omits one-timediscover; full/compact cold = warm. Compactfile-explorationskipsfiles.list(no compact op).

This project uses GitHub Spec Kit for non-trivial feature planning.

For meaningful behavior changes, new MCP tools, schema changes, configuration changes, or changes that affect agent-facing behavior, contributors should start from the project constitution:

- specs/FEATURE/spec.md
- specs/FEATURE/plan.md
- specs/FEATURE/tasks.md

Small bug fixes, documentation edits, dependency bumps, and mechanical refactors do not require a full Spec Kit workflow unless they affect the public MCP contract.

All changes must preserve the MCP contract, OpenGrok semantics, security posture, compatibility expectations, and documentation requirements described in the constitution.

- Large project traversal is bounded, and some search and discovery operations are best-effort rather than language-semantic.
- HTTP transport is intended for controlled local or internal setups and does not add inbound client authentication.

opengrok-go-mcpis licensed under the Apache License 2.0 (Apache-2.0) for new releases starting withv0.3.0-beta.2.

Earlier published releases up to and includingv0.3.0-beta.1were released underCC0-1.0and remain available under those terms.

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