# compare_snapshots

Compares two saved render snapshots and shows per-component render count changes.

Agent View of the PolicyLayer registry record for `compare_snapshots`. HTML page: https://policylayer.com/tools/0x1f320-why-did-you-render-mcp/compare-snapshots

## Facts

- Tool: `compare_snapshots`
- Server: Why Did You Render (`0x1f320/why-did-you-render-mcp`) — https://policylayer.com/tools/0x1f320-why-did-you-render-mcp.md
- Homepage: https://github.com/0x1f320/why-did-you-render-mcp
- 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": "compare_snapshots",
    "arguments": {}
  }
}
```

## Why compare_snapshots is rated Low

This tool retrieves and analyzes existing snapshot data to display comparative metrics. It is purely observational with no side effects—it reads performance data and presents differences between two snapshots. No data is modified, deleted, or executed. This is a diagnostic/reporting function characteristic of Read category tools.

From the tool's own definition: "Tool name and description indicate data retrieval and comparison: 'compares two saved render snapshots and shows per-component render count changes.' No creation, modification, deletion, or execution of external operations occurs."

## Use case

AI agents call compare_snapshots to retrieve information from Why Did You Render 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 Why Did You Render:

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

## Other tools on Why Did You Render (13)

- `clear_renders` — Destructive — https://policylayer.com/tools/0x1f320-why-did-you-render-mcp/clear-renders.md
- `delete_snapshot` — Destructive — https://policylayer.com/tools/0x1f320-why-did-you-render-mcp/delete-snapshot.md
- `pause_renders` — Execute — https://policylayer.com/tools/0x1f320-why-did-you-render-mcp/pause-renders.md
- `wait_for_renders` — Execute — https://policylayer.com/tools/0x1f320-why-did-you-render-mcp/wait-for-renders.md
- `get_commits` — Read — https://policylayer.com/tools/0x1f320-why-did-you-render-mcp/get-commits.md
- `get_projects` — Read — https://policylayer.com/tools/0x1f320-why-did-you-render-mcp/get-projects.md
- `get_render_summary` — Read — https://policylayer.com/tools/0x1f320-why-did-you-render-mcp/get-render-summary.md
- `get_renders` — Read — https://policylayer.com/tools/0x1f320-why-did-you-render-mcp/get-renders.md
- `get_renders_by_commit` — Read — https://policylayer.com/tools/0x1f320-why-did-you-render-mcp/get-renders-by-commit.md
- `get_tracked_components` — Read — https://policylayer.com/tools/0x1f320-why-did-you-render-mcp/get-tracked-components.md
- `list_snapshots` — Read — https://policylayer.com/tools/0x1f320-why-did-you-render-mcp/list-snapshots.md
- `resume_renders` — Write — https://policylayer.com/tools/0x1f320-why-did-you-render-mcp/resume-renders.md
- `save_snapshot` — Write — https://policylayer.com/tools/0x1f320-why-did-you-render-mcp/save-snapshot.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=0x1f320-why-did-you-render-mcp · API: https://policylayer.com/registry/api · Policy library: https://policylayer.com/policies/0x1f320-why-did-you-render-mcp