Schema minimize & catalog pin

Opt-in controls that address context-window bloat and tool-poisoning drift without changing Bastion’s zero-infra nature (no embeddings, no new heavy deps).

Schema minimization

Shrink verbose tools/list manifests while keeping the same tools:

discovery_filter:
  enabled: false          # allowlist strip is separate
  minimize_schemas: true  # default false
  max_description_chars: 160
  strip_schema_descriptions: true

• Truncates each tool description
• Recursively removes description keys inside inputSchema / input_schema
• Records estimated tokens_saved under FinOps metrics (source=schema_minimize)

Pair with discovery_filter.enabled + tool_allowlist when you also want fewer tools advertised.

Live catalog pin

Runtime enforcement of tool metadata fingerprints (ROADMAP P1):

tool_metadata_fingerprint:
  enabled: true
  pin_on_first_seen: true   # first tools/list becomes the pin
  on_drift: block           # warn | block
  pin_ttl_seconds: 604800   # 7 days (memory / Redis state_backend)

Or pin to a known hash / fingerprint file:

tool_metadata_fingerprint:
  enabled: true
  fingerprint_path: tools.fingerprint.json   # from `mcp-bastion fingerprint`
  on_drift: block

• Runs on tools/list after allowlist discovery filter, before schema minimize (full metadata hashed)
• warn: allow response, set catalog_drift_warnings metadata
• block: raise CatalogDriftError (-32032)
• Multi-replica: use state_backend.type: redis

Related

• FEATURES.md
• BENCHMARKS.md - discovery filter token savings
• mcp-bastion fingerprint / mcp-bastion scan