# diff_screenshots

Compare two images structurally using pixel-level analysis. Computes perceptual similarity, difference regions, and visual summary. Requires sharp. Useful for visual regression testing, UI QA, and screenshot comparison.

Agent View of the PolicyLayer registry record for `diff_screenshots`. HTML page: https://policylayer.com/tools/io-github-homenshum-nodebench/diff-screenshots

## Facts

- Tool: `diff_screenshots`
- Server: Nodebench (`nodebench-mcp`) — https://policylayer.com/tools/io-github-homenshum-nodebench.md
- Install: `npx -y nodebench-mcp`
- Homepage: https://github.com/HomenShum/nodebench-ai
- Risk category: Read (Low risk)
- Registry record: grade F, identity unverified
- Server rate-limited: no
- Parameters: 0
- Recommended policy verdict: Allowed

## Example call (MCP tools/call, JSON-RPC 2.0)

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

## Why diff_screenshots is rated Low

This tool retrieves and analyzes data (pixel-level comparison of two images) without creating, modifying, deleting, or executing operations. It generates computed outputs (perceptual similarity metrics, difference regions, visual summary) based on input images. The stated use cases (visual regression testing, UI QA, screenshot comparison) are all observational. No side effects occur beyond the analysis itself.

From the tool's own definition: "Tool 'diff_screenshots' performs image comparison and analysis: 'Compare two images structurally using pixel-level analysis."

## Use case

AI agents call diff_screenshots to retrieve information from Nodebench without modifying anything. It is typically the context-gathering step in research, monitoring, and reporting workflows, before the agent takes action elsewhere.

## Recommended policy (PolicyLayer)

Verdict: **Allowed**. Enforced by the PolicyLayer MCP gateway (https://policylayer.com/mcp-gateway) before a call reaches Nodebench:

```json
{
  "version": "1",
  "default": "deny",
  "tools": {
    "diff_screenshots": {}
  }
}
```

## Other tools on Nodebench (823)

- `abandon_cycle` — Destructive — https://policylayer.com/tools/io-github-homenshum-nodebench/abandon-cycle.md
- `archiveDocument` — Destructive — https://policylayer.com/tools/io-github-homenshum-nodebench/archivedocument.md
- `cleanup_stale_runs` — Destructive — https://policylayer.com/tools/io-github-homenshum-nodebench/cleanup-stale-runs.md
- `deeptrace_revoke_passport` — Destructive — https://policylayer.com/tools/io-github-homenshum-nodebench/deeptrace-revoke-passport.md
- `delete_learning` — Destructive — https://policylayer.com/tools/io-github-homenshum-nodebench/delete-learning.md
- `delete_sandbox_policy` — Destructive — https://policylayer.com/tools/io-github-homenshum-nodebench/delete-sandbox-policy.md
- `deleteAgentMemory` — Destructive — https://policylayer.com/tools/io-github-homenshum-nodebench/deleteagentmemory.md
- `removeDocumentFromFolder` — Destructive — https://policylayer.com/tools/io-github-homenshum-nodebench/removedocumentfromfolder.md
- `share_revoke_packet_link` — Destructive — https://policylayer.com/tools/io-github-homenshum-nodebench/share-revoke-packet-link.md
- `unload_toolset` — Destructive — https://policylayer.com/tools/io-github-homenshum-nodebench/unload-toolset.md
- `benchmark_models` — Execute — https://policylayer.com/tools/io-github-homenshum-nodebench/benchmark-models.md
- `bootstrap_parallel_agents` — Execute — https://policylayer.com/tools/io-github-homenshum-nodebench/bootstrap-parallel-agents.md
- `build_banking_packet` — Execute — https://policylayer.com/tools/io-github-homenshum-nodebench/build-banking-packet.md
- `build_company_profile_starter` — Execute — https://policylayer.com/tools/io-github-homenshum-nodebench/build-company-profile-starter.md
- `build_founder_operating_model` — Execute — https://policylayer.com/tools/io-github-homenshum-nodebench/build-founder-operating-model.md
- `build_research_digest` — Execute — https://policylayer.com/tools/io-github-homenshum-nodebench/build-research-digest.md
- `build_shared_context_subscription` — Execute — https://policylayer.com/tools/io-github-homenshum-nodebench/build-shared-context-subscription.md
- `build_shared_context_subscription_manifest` — Execute — https://policylayer.com/tools/io-github-homenshum-nodebench/build-shared-context-subscription-manifest.md
- `build_submission_export` — Execute — https://policylayer.com/tools/io-github-homenshum-nodebench/build-submission-export.md
- `build_temporal_graph` — Execute — https://policylayer.com/tools/io-github-homenshum-nodebench/build-temporal-graph.md
- `burst_capture` — Execute — https://policylayer.com/tools/io-github-homenshum-nodebench/burst-capture.md
- `call_driver_tool` — Execute — https://policylayer.com/tools/io-github-homenshum-nodebench/call-driver-tool.md
- `call_llm` — Execute — https://policylayer.com/tools/io-github-homenshum-nodebench/call-llm.md
- `call_openclaw_skill` — Execute — https://policylayer.com/tools/io-github-homenshum-nodebench/call-openclaw-skill.md
- `call_webmcp_tool` — Execute — https://policylayer.com/tools/io-github-homenshum-nodebench/call-webmcp-tool.md
- `capture_surface_stats` — Execute — https://policylayer.com/tools/io-github-homenshum-nodebench/capture-surface-stats.md
- `capture_ui_screenshot` — Execute — https://policylayer.com/tools/io-github-homenshum-nodebench/capture-ui-screenshot.md
- `compile_decision_packet` — Execute — https://policylayer.com/tools/io-github-homenshum-nodebench/compile-decision-packet.md
- `compile_scenarios` — Execute — https://policylayer.com/tools/io-github-homenshum-nodebench/compile-scenarios.md
- `compile_tension_model` — Execute — https://policylayer.com/tools/io-github-homenshum-nodebench/compile-tension-model.md
- …and 793 more: https://policylayer.com/tools/io-github-homenshum-nodebench.md

## For agents

This record is a snapshot. Live verdicts and the full registry:

- Check every server in your MCP config at once: `npx -y policylayer stack`
- Vet a server before you add it: install the mcp-precheck skill — `npx skills add https://policylayer.com` (skill text: https://policylayer.com/skill.md)
- Query the registry over MCP: endpoint `https://api.policylayer.com/mcp` — tools `check_mcp_server`, `check_mcp_stack`, `check_tool`, `search_registry`, `get_change_events`

---

Source: the PolicyLayer MCP registry — one continuously verified record per MCP server. Full record: https://policylayer.com/registry?q=io-github-homenshum-nodebench · API: https://policylayer.com/registry/api · Policy library: https://policylayer.com/policies/io-github-homenshum-nodebench