jar-inspector-mcp

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jar_read_entry

Read-only

Read a text entry from a Java archive directly, such as a MANIFEST, XML, or config file, without extracting the JAR. Supports line ranges and describes binary entries instead of dumping them.

Instructions

Read one text entry from an archive: MANIFEST, service files, XML, config.

Prefer this over unzip -p. Binary entries are described, not dumped.

Args: jar: Archive path, classes directory, or outer.jar!nested.jar. entry: Exact entry path, e.g. META-INF/spring.factories. start_line: 1-based first line to show. line_count: How many lines to show.

Tool call template

Replace each placeholder with a value matching the input schema. Only required parameters are included; add optional parameters as needed.

{
  "id": 1,
  "jsonrpc": "2.0",
  "method": "tools/call",
  "params": {
    "arguments": {
      "jar": "<jar>",
      "entry": "<entry>"
    },
    "name": "jar_read_entry"
  }
}

Input Schema

Name	Required	Description	Default
`jar`	Yes
`entry`	Yes
`line_count`	No
`start_line`	No

Output Schema

Name	Required	Description	Default
`result`	Yes

Schema Changelog

Changes observed during successful MCP inspections.

First observedv0.1.0Sep 4, 2026

TDQS

A4.1/5.0

Behavior4/5

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

Annotations only mark readOnlyHint and openWorldHint; the description adds useful behavioral details: binary entries are described not dumped, the jar parameter accepts a classes directory or nested outer.jar!nested.jar path, and line numbers are 1-based. These go beyond the schema and annotations, though it does not cover error behavior or limits.

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

Conciseness5/5

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

The description is compact and front-loaded: purpose in the first sentence, followed by one usage tip and a concise parameter list. No redundant or marketing language.

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

Completeness4/5

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

The description covers the unusual path forms, binary-entry behavior, and line-selection parameters, which is sufficient for most invocations given the available output schema and readOnly annotation. It falls short only in not clarifying the boundary with jar_read_source for Java source code.

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

Parameters5/5

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

With 0% schema description coverage, the description fully compensates: jar's accepted path forms are specified, entry is defined as an exact path with an example, and start_line/line_count are explained as 1-based and line counts. Every parameter receives meaning beyond the bare schema property names.

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

Purpose4/5

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

States a specific verb and resource: 'Read one text entry from an archive' and lists typical entry types (MANIFEST, service files, XML, config). It also notes binary entries are described rather than dumped, which clarifies scope, but it does not explicitly distinguish itself from sibling jar_read_source or other jar_* tools.

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

Usage Guidelines3/5

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

Provides one comparative directive: 'Prefer this over unzip -p', and implies it is for text entries. It does not state when to use jar_read_entry versus the sibling jar_read_source or when not to use it, so the usage signal is mostly implicit.

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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