npm-mcp

diff

Diff npm packages: compare two package versions, or a local package against its published registry version. Specify versions via range or array, or provide local path.

Instructions

Show diff between package versions or between local and registry

Tool call template

This tool declares no required parameters. Add optional parameters from the input schema as needed.

{
  "id": 1,
  "jsonrpc": "2.0",
  "method": "tools/call",
  "params": {
    "arguments": {},
    "name": "diff"
  }
}

Input Schema

Name	Required	Description
`path`	No	Absolute path to local package (compares local vs registry)
`specs`	No	Two package specs to compare (e.g. ['pkg@1.0.0', 'pkg@2.0.0'])
`package`	No	Package spec for comparison (e.g. pkg@1.0.0..pkg@2.0.0)
`diffNameOnly`	No	Only show file names that changed

Schema Changelog

Changes observed during successful MCP inspections.

First observedv1.2.1Mar 19, 2026

TDQS

B3.1/5.0

Behavior2/5

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

No annotations provided, and description lacks behavioral details. It doesn't state if the tool is read-only, fetches registry data, or has side effects. The agent cannot infer safety or network usage.

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

Conciseness4/5

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

Single 12-word sentence that front-loads the verb and resource. No wasted words, though slightly more structure (e.g., listing modes) could improve readability without adding length.

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

Completeness2/5

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

With 4 parameters, no output schema, and no annotations, the description is insufficient. It doesn't explain the two comparison modes (package spec vs local path) or the behavior of 'diffNameOnly'.

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

Parameters3/5

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

Schema coverage is 100% with parameter descriptions. The description adds no extra meaning beyond the schema, meeting the baseline for high coverage.

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?

Description clearly states verb 'show diff' and resources 'package versions' or 'local vs registry'. This distinguishes it from sibling tools like 'version', 'publish', or 'view'.

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

Usage Guidelines2/5

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

No guidance on when to use diff vs alternatives. For example, it doesn't mention that 'view' shows current version or 'outdated' lists newer versions, leaving the agent to guess.

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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