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find_implementations

Locate all implementors of an interface or subclasses of a class from a Java file position, returning each implementing or extending type with its location.

Instructions

Find implementations of an interface or extensions of a class.

USAGE: Position on a type (interface or class), find all implementors/subclasses OUTPUT: List of implementing/extending types with locations

IMPORTANT: Uses ZERO-BASED coordinates.

potentialMatches are the places naming the type, or one of its subtypes, as a supertype that JDT could not confirm: the class declaring each may be an implementation, and, for a method, may override it.

maxResults outside 0 to 1000 is INVALID_PARAMETER.

potentialMatches, present only when there are any, holds the places JDT's search reports as possible matches but cannot confirm, because a type or name there does not resolve (a missing dependency or a compile error): count is their exact number, and locations lists them, as many as the results it stands beside may list. They are never counted or listed as results.

Requires load_project to be called first.

Input Schema

NameRequiredDescriptionDefault
lineYesZero-based line number
columnYesZero-based column number
filePathYesPath to source file
maxResultsNoMax implementations to return, 0 to 1000 (default 100)

Schema Changelog

Changes observed during successful MCP inspections.

  1. Changed1 schema field changedv1.5.3
    • changedInput schema / properties / maxResults / description
      Previous value: -"Max implementations to return (default 100)"New value: +"Max implementations to return, 0 to 1000 (default 100)"
  2. Addedv1.3.4
  3. Removedv1.3.3
  4. First observedv1.2.0

TDQS

A4.5/5.0
Behavior5/5

Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?

With no annotations, the description carries the full behavioral burden and does so thoroughly: it explains zero-based coordinates, maxResults validation ('outside 0 to 1000 is INVALID_PARAMETER'), the prerequisite load_project, and detailed semantics of potentialMatches including when it is present and why matches may be unconfirmed.

Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

Conciseness3/5

Is the description appropriately sized, front-loaded, and free of redundancy?

The description is front-loaded with purpose, usage, and output, which is good. However, the explanation of potentialMatches is repetitive: it appears once as 'potentialMatches are the places...' and again in a longer paragraph, without enough added clarity to justify the duplication.

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Completeness5/5

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

For a 4-parameter tool with no output schema and no annotations, the description supplies everything needed: purpose, usage, output summary, coordinate convention, parameter constraints, prerequisite, and the special potentialMatches behavior. Nothing essential is missing.

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Parameters4/5

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

Schema description coverage is 100%, so the baseline is 3. The description adds meaning beyond the schema by specifying that maxResults outside 0 to 1000 is an INVALID_PARAMETER error and by reinforcing the zero-based coordinate convention for line and column.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Purpose5/5

Does the description clearly state what the tool does and how it differs from similar tools?

The description states a specific verb and resource: 'Find implementations of an interface or extensions of a class.' This is distinct from sibling tools like find_references or get_type_hierarchy, and the agent can identify the operation directly from the first sentence.

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Usage Guidelines4/5

Does the description explain when to use this tool, when not to, or what alternatives exist?

The description provides clear invocation context with 'USAGE: Position on a type (interface or class), find all implementors/subclasses' and a prerequisite: 'Requires load_project to be called first.' It does not explicitly name alternatives or when-not conditions, but the context is sufficient for correct use.

Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.

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