git-prism

Agent-optimized git data for LLM agents. Three MCP tools that replace human-oriented diffs with structured JSON -- function-level granularity, import tracking, dependency changes, complete file snapshots, and per-commit history.

The Problem

Git's porcelain output (diff, log, --stat) is designed for human eyes. When an LLM agent parses a unified diff, it burns tokens on @@ hunk headers, +/- line prefixes, and whitespace context that carries no semantic meaning. Worse, it has to reconstruct what actually changed -- which functions were modified, which imports were added, whether the file is generated -- from raw text.

git-prism gives agents structured data directly: a change manifest with per-file metadata and function-level analysis, plus full before/after file content when deeper inspection is needed.

Installation

From crates.io (recommended)

cargo install git-prism

From source

cargo install --path .

Binary download

Grab a prebuilt binary from the GitHub Releases page.

Homebrew (macOS and Linux)

brew tap mikelane/tap
brew install git-prism

MCP Registration

Register git-prism as an MCP server for Claude Code:

claude mcp add git-prism -- git-prism serve

That's it. The server uses stdio transport and is available in all Claude Code sessions.

Tools

get_change_manifest

Returns structured metadata about what changed between two git refs.

Parameters:

Example output:

{
  "metadata": {
    "repo_path": "/home/user/myproject",
    "base_ref": "main",
    "head_ref": "HEAD",
    "base_sha": "a1b2c3d4e5f6",
    "head_sha": "f6e5d4c3b2a1",
    "generated_at": "2026-04-03T12:00:00Z",
    "version": "0.1.0"
  },
  "summary": {
    "total_files_changed": 3,
    "files_added": 1,
    "files_modified": 2,
    "files_deleted": 0,
    "files_renamed": 0,
    "total_lines_added": 47,
    "total_lines_removed": 12,
    "total_functions_changed": 4,
    "languages_affected": ["go", "rust"]
  },
  "files": [
    {
      "path": "src/handler.go",
      "old_path": null,
      "change_type": "modified",
      "language": "go",
      "is_binary": false,
      "is_generated": false,
      "lines_added": 25,
      "lines_removed": 8,
      "size_before": 1200,
      "size_after": 1450,
      "functions_changed": [
        {
          "name": "HandleRequest",
          "change_type": "signature_changed",
          "start_line": 15,
          "end_line": 42,
          "signature": "func HandleRequest(ctx context.Context, req *Request) (*Response, error)"
        },
        {
          "name": "validateInput",
          "change_type": "added",
          "start_line": 44,
          "end_line": 58,
          "signature": "func validateInput(req *Request) error"
        }
      ],
      "imports_changed": {
        "added": ["context", "errors"],
        "removed": ["log"]
      }
    }
  ],
  "dependency_changes": [
    {
      "file": "go.mod",
      "added": [{"name": "github.com/pkg/errors", "old_version": null, "new_version": "v0.9.1"}],
      "removed": [],
      "changed": []
    }
  ],
  "truncated": false,
  "truncation_info": null
}

get_file_snapshots

Returns complete before/after file content at two git refs. No diffs to parse -- the agent gets the full file at each point in time.

Parameters:

Example output:

{
  "metadata": {
    "repo_path": "/home/user/myproject",
    "base_ref": "main",
    "head_ref": "HEAD",
    "generated_at": "2026-04-03T12:00:00Z"
  },
  "files": [
    {
      "path": "src/handler.go",
      "language": "go",
      "is_binary": false,
      "before": {
        "content": "package main\n\nfunc HandleRequest(req *Request) error {\n    // old implementation\n}\n",
        "line_count": 5,
        "size_bytes": 82,
        "truncated": false
      },
      "after": {
        "content": "package main\n\nimport \"context\"\n\nfunc HandleRequest(ctx context.Context, req *Request) (*Response, error) {\n    // new implementation\n}\n",
        "line_count": 7,
        "size_bytes": 130,
        "truncated": false
      },
      "error": null
    }
  ],
  "token_estimate": 53
}

get_commit_history

Returns one manifest per commit in a range, so agents can see what changed in each commit separately instead of a single collapsed diff.

Parameters:

Example output:

{
  "commits": [
    {
      "metadata": {
        "sha": "a1b2c3d4",
        "message": "add validation helper",
        "author": "Jane Dev",
        "timestamp": "2026-04-03T10:30:00+00:00"
      },
      "files": [
        {
          "path": "src/validate.rs",
          "change_type": "added",
          "language": "rust",
          "lines_added": 25,
          "lines_removed": 0
        }
      ],
      "summary": {
        "total_files_changed": 1,
        "files_added": 1,
        "total_lines_added": 25,
        "total_lines_removed": 0
      }
    }
  ]
}

CLI Usage

git-prism also works as a standalone CLI for scripting and debugging:

# Change manifest between two refs
git-prism manifest HEAD~1..HEAD

# Manifest for a specific repo path
git-prism manifest main..feature-branch --repo /path/to/repo

# Per-commit history for a range
git-prism history HEAD~5..HEAD

# File snapshots for specific paths
git-prism snapshot HEAD~3..HEAD --paths src/main.rs src/lib.rs

# List supported languages
git-prism languages

The manifest, snapshot, and history commands output JSON to stdout. The languages command outputs plain text.

Agent Workflow

The typical agent pattern is two calls -- triage, then deep dive:

Step 1: Triage with get_change_manifest

Ask for the manifest to understand the shape of a change. The summary tells you file counts, line counts, and affected languages. The per-file entries tell you which functions changed signatures, which imports were added, and whether files are generated (safe to skip).

Step 2: Deep dive with get_file_snapshots

Once you know which files matter, request full snapshots of just those files. You get complete before/after content -- no reconstructing files from diff hunks. Use line_range to focus on specific sections and include_before: false when you only need the current state.

This two-step approach keeps token usage low. The manifest is compact metadata; snapshots are requested only for files that need inspection.

Supported Languages

Function-level analysis uses tree-sitter to extract functions, methods, and imports from source code.

Files in unsupported languages still appear in the manifest with full line/size/change-type metadata -- functions_changed is null (not an empty array) to distinguish "no grammar available" from "analyzed, nothing changed."

Dependency File Tracking

git-prism parses dependency files and reports added, removed, and version-changed packages:

• Cargo.toml (Rust)
• package.json (Node.js)
• go.mod (Go)
• pyproject.toml (Python, PEP 621)

Contributing

See CONTRIBUTING.md.

License

Apache-2.0