Maven Code Search

Overview

Use the maven-decoder MCP server before guessing about third-party Java dependencies. It can search the user's installed Maven repository, search Maven Central online, inspect jars, prefer source jars when available, and decompile bytecode when source is missing.

The MCP sees both local and remote artifacts. Artifacts already in the local Maven repository are used directly; anything else is downloaded from Maven Central into a separate cache on demand, so you can inspect a library the user has never installed. Local copies always take precedence.

If a remote lookup fails, check whether offline mode is enabled (MAVEN_OFFLINE) before telling the user an artifact does not exist.

Quick Workflow

1. Identify the target coordinates when possible: group_id, artifact_id, and version. Read pom.xml, build.gradle, lockfiles, or existing imports if the user did not provide them.
2. Use MCP search tools to confirm what is available before inspecting code. Search locally first; go online when the artifact is not installed.
3. Prefer narrow queries: a class name, package pattern, artifact coordinates, or method pattern.
4. Use pagination for broad searches and ask for the next page only when the current page is not enough.
5. Report findings with exact coordinates, class names, method names, whether the result came from sources or decompiled bytecode, and whether it came from the local repository or was downloaded.

Tool Selection

Local first

Use list_artifacts to discover installed artifacts or filter by partial group_id, artifact_id, or version.

Use get_version_info when the user asks which versions of an artifact are installed. Set include_remote: true to also show versions published on Maven Central.

Use search_classes when the user knows a class name, simple type name, wildcard, or package but not the artifact that contains it. This scans installed jars only.

Going online

Use search_maven_central when the artifact is not installed, when the user asks what exists on Maven Central, or when search_classes finds nothing. Search by class_name or fully_qualified_class to discover which published artifact contains a type.

Use get_remote_versions when the user asks what versions exist, which is the newest, or whether an upgrade is available. This reads maven-metadata.xml and keeps working even when the search index is throttled.

Use download_artifact to pull an artifact into the cache before a deep inspection. Pass latest as the version to get the newest release. This is usually optional: the analysis tools download automatically when an artifact is missing.

Inspecting code (local or downloaded)

Use extract_class_info when the user needs constructors, fields, annotations, or method signatures for classes in a known artifact. If sources are missing, this tool still returns bytecode-backed fields and methods through the MCP, so do not shell out to javap for the same information.

Use extract_source_code when the user needs implementation details. Set prefer_sources to true unless there is a specific reason to force decompilation.

Use extract_jar_resource when the user needs files embedded in the jar, such as .proto files, service descriptors, or Maven metadata. Use analyze_jar first when you need to discover resource paths. Do not shell out to jar tf just to list or read jar entries.

Use extract_method_info for targeted method inspection instead of pulling a large class.

Use get_dependencies for direct POM dependencies and get_dependency_tree for transitive dependency chains.

Use find_dependents when the user asks "what installed artifacts depend on X?"

Use compare_versions when the user asks what changed between two versions, or whether an upgrade is safe. With compare_api (default true) it returns added and removed public/protected members per class, a breaking_changes count, and a compatible flag. Report removals as the risk, and mention that a member which moved to a supertype still shows as removed.

Use analyze_jar or analyze_jar_structure when the user asks about jar metadata, manifests, packages, resources, services, or high-level structure.

Use find_usage_examples when the user asks how a class or method is used, or which installed artifacts call it. It scans bytecode references, so it finds real callers rather than guesses, and ranks test jars first. Pass method_name to narrow to a specific call.

Use search_classes with annotation to find classes carrying an annotation, such as Deprecated or a Spring stereotype. The annotation may be a simple name, a fully qualified name, or a pattern.

Query Patterns

For "Where is ObjectMapper installed?", call search_classes with class_name: "ObjectMapper" and inspect the returned artifact coordinates. If nothing is installed, call search_maven_central with the same class name to find the published artifact.

For "What library provides X?" when nothing is installed, call search_maven_central with class_name or fully_qualified_class, then inspect the best match directly; it will be downloaded automatically.

For "Is there a newer version of X?", call get_remote_versions and compare against the version in the project's build file.

For "Show me the methods on RestTemplate", first resolve the artifact/version if needed, then call extract_class_info with the fully qualified class name or a precise class pattern.

For "How does this library implement retry?", search for likely classes by package or class name, then use extract_method_info or extract_source_code on the most relevant classes.

For generated protobuf classes with no sources jar, call extract_class_info on the generated class to recover parsed methods and fields. If the jar includes .proto resources or descriptor metadata, use analyze_jar and extract_jar_resource to inspect those resources through the MCP.

For "Why do I have two versions?", use get_dependency_tree, find_dependents, and compare_versions as needed. Tie the answer back to the project's declared dependencies.

Answer Guidelines

Keep responses grounded in MCP results. Include:

• Maven coordinates, including version.
• Fully qualified class or method names.
• Whether source came from a source jar or decompilation when that distinction is visible.
• Whether the artifact was already installed locally or was downloaded from Maven Central. The origin field in responses reports this as local-repository or remote-cache.
• Pagination status when results are incomplete.
• For compiled-only classes, say that the class details came from bytecode-backed MCP inspection rather than claiming the source jar was available.

Do not claim an artifact or version does not exist based only on a local search. Confirm with search_maven_central or get_remote_versions first, unless offline mode is enabled.

Do not paste huge decompiled files into chat. Summarize the relevant behavior and include only small snippets when they are necessary to explain the answer.

Missing MCP Server

If the maven-decoder MCP tools are not available, tell the user the skill requires the Maven Decoder MCP server to be installed and configured in their MCP-capable client. A common stdio setup is:

{
  "maven-decoder": {
    "command": "uvx",
    "args": ["maven-decoder-mcp"]
  }
}