Context Surface Analyzer

A local, deterministic utility for measuring one explicit Agent tool-catalog snapshot and comparing two snapshots.

It reports canonical UTF-8 bytes and SHA-256 digests, tool/schema counts, exact duplicate schemas, hard name collisions, declared budget checks, and deltas. Optional token counts remain externally measured and fully labeled; the product does not infer tokens from bytes or decide whether a tool is useful.

Run

Requires Node.js 22 or newer and has no third-party runtime dependencies.

npm run check
node src/cli.js analyze examples/baseline.json
node src/cli.js diff examples/baseline.json examples/updated.json
npm start

The web surface opens at http://127.0.0.1:4173. Use --port 0 to select an ephemeral port. A snapshot can be pasted or loaded from a bounded local JSON file; the browser does not retain it after the page is closed.

Snapshot authority

Acquire each snapshot from the current provider, host, or an authorized exporter. This product deliberately does not discover a host, start arbitrary MCP servers, crawl files, or treat repository fixtures as the current installed catalog. Project the exported catalog into the closed context-surface.snapshot.v0.1 format before analysis and retain the exporter, provider, and revision as the source of record.

MCP

Start the newline-delimited JSON-RPC stdio server:

npm run mcp

It exposes two read-only tools:

• context.analyze: one snapshot to one analysis;
• context.diff: earlier and later snapshots to one comparison.

Both accept snapshot JSON as bounded strings, so the Agent route has no ambient filesystem authority. See the product model for the snapshot contract and exact semantics.

This portable runtime intentionally serves the MCP 2025 legacy era through revision 2025-11-25. Dual-era clients can identify that boundary from the server/discover method-not-found response and fall back to initialize. Modern-only 2026 transport is not claimed by this dependency-free plugin.

Local Codex plugin

Build and validate the repository-local plugin, add this repository as a local marketplace, then install the plugin:

npm run check
codex plugin marketplace add <repository-root>
codex plugin add context-surface-analyzer@context-surface-analyzer

Start a new Codex task after installation so the Skill and MCP tools are loaded from the same cached plugin version.

Status

This is a local MVP. Development checks, direct runtime probes, installed Codex routing, production load behavior, public-release readiness, and owner visual acceptance remain separate claims. See the review contract and the first real-catalog dogfood note.

License

Apache License 2.0. See LICENSE and NOTICE.