lsp-implement

Requires the agent-lsp MCP server.

lsp-implement

Find every concrete type that implements an interface, or every subtype of an abstract type. Read-only — does not modify any files.

Use this skill before changing an interface signature, adding a method to an interface, or removing a base-type method. It tells you every type that must be updated.

Invocation: User provides type_name (e.g. "Handler", "io.Reader"). Optionally provide workspace_root.

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Prerequisites

Check server capabilities — go_to_implementation and type_hierarchy are optional features not implemented by all language servers:

mcp__lsp__get_server_capabilities()

Note which of go_to_implementation and type_hierarchy appear in supported_tools. The steps below depend on this result.

If neither is supported, report "Server does not support implementation lookup" and stop.

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Step 1 — Locate the interface or type

mcp__lsp__go_to_symbol({
  "symbol_path": "<TypeName>",
  "workspace_root": "/abs/path"   // optional
})
→ returns: file, line, column (1-indexed)

Open the file so the language server tracks it:

mcp__lsp__open_document({
  "file_path": "<file from go_to_symbol>"
})

Record file, line, column for subsequent steps.

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Step 2 — Find all implementations

Only if go_to_implementation appears in supported_tools.

mcp__lsp__go_to_implementation({
  "file_path": "<file>",
  "line": <line>,
  "column": <column>
})

Returns a list of locations — each is a concrete type that satisfies the interface. Group by file. Record type names and locations.

If go_to_implementation is not supported: skip; note in report.

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Step 3 — Type hierarchy (subtypes and supertypes)

Only if type_hierarchy appears in supported_tools.

mcp__lsp__type_hierarchy({
  "file_path": "<file>",
  "line": <line>,
  "column": <column>,
  "direction": "subtypes"   // use "both" to also see what this type extends
})

subtypes returns concrete types that extend or embed this type. supertypes returns what this type itself implements.