docs(readme): note auto-emitted compatible_clients on build_agent_instructions

The challenge subpath table didn't surface the auto-emitted per-rail
compatible_clients field. Add a parenthetical so vendors evaluating the
SDK see this without reading source.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

Author: vvillait88

README.md

@@ -19,7 +19,7 @@ pip install agentscore-commerce[fastapi]   # or [flask], [django], [aiohttp], [s
 | `agentscore_commerce.identity` (package level) | Re-exports the denial helpers: `denial_reason_status`, `denial_reason_to_body`, `build_signer_mismatch_body`, `build_contact_support_next_steps`, `verification_agent_instructions`, `is_fixable_denial`, `FIXABLE_DENIAL_REASONS`. Also re-exports the per-product policy helpers: `PolicyBlock`, `GateResult`, `EnforcementMode`, `IdentityStatus`, `build_gate_from_policy`, `run_gate_with_enforcement`, `shipping_country_allowed`, `shipping_state_allowed` — for multi-product merchants where each product carries its own compliance config (hard gate vs soft vs none, per-product shipping allowlists). |
 | `agentscore_commerce.payment` | `networks`, `USDC`, `rails` registries; `payment_directive`, `build_payment_directive`, `www_authenticate_header`, `payment_required_header`, `alias_amount_fields` (v1↔v2 amount field shim — emits both `amount` and `maxAmountRequired` so v1-only x402 parsers like Coinbase awal can read v2 bodies), `settlement_override_header`, `dispatch_settlement_by_network`, `extract_payment_signer` (returns `PaymentSigner({address, network})`), `register_x402_schemes_v1_v2`; drop-in x402 helpers: `validate_x402_network_config` (boot-time guard), `verify_x402_request` (parse + validate inbound X-Payment), `process_x402_settle` (verify-then-settle with one call). |
 | `agentscore_commerce.discovery` | `is_discovery_probe_request`, `build_discovery_probe_response` (with optional `x402_sample` for x402-aware crawlers — `awal x402 details` etc.), `sample_x402_accept_for_network` (USDC sample-accept builder for known CAIP-2 networks), `build_well_known_mpp`, `build_llms_txt` + `llms_txt_identity_section` + `llms_txt_payment_section` (compact + verbose modes), `agentscore_openapi_snippets`, `build_bazaar_discovery_payload`, `NoindexNonDiscoveryMiddleware` (ASGI middleware that emits `X-Robots-Tag: noindex` on every path except the agent-discovery surfaces — defaults cover `/openapi.json`, `/llms.txt`, `/.well-known/{mpp.json,agent-card.json,ucp}`, `/favicon.{png,ico}`; pure helpers `is_discovery_path` + `DEFAULT_DISCOVERY_PATHS` for non-ASGI frameworks). |
-| `agentscore_commerce.challenge` | `build_402_body`, `build_accepted_methods`, `build_identity_metadata`, `build_how_to_pay`, `build_agent_instructions`, `build_pricing_block` (cents → dollar-string with optional shipping/tax), `first_encounter_agent_memory` (cross-merchant hint, returns the canonical block or `None` based on a per-merchant first-seen flag), `OrderReceipt` (dataclass for the post-settlement 200 response shape); `respond_402` — drop-in 402 emit that preserves pympp's `WWW-Authenticate` and layers x402's `PAYMENT-REQUIRED`. `build_validation_error` — structured 4xx body builder (`{error: {code, message}, required_fields?, example_body?, next_steps?, ...extra}`) so vendors compose body shapes by name instead of inlining at every validation site. |
+| `agentscore_commerce.challenge` | `build_402_body`, `build_accepted_methods`, `build_identity_metadata`, `build_how_to_pay`, `build_agent_instructions` (auto-emits per-rail `compatible_clients` — smoke-verified CLIs the agent should use; vendor override supported), `build_pricing_block` (cents → dollar-string with optional shipping/tax), `first_encounter_agent_memory` (cross-merchant hint, returns the canonical block or `None` based on a per-merchant first-seen flag), `OrderReceipt` (dataclass for the post-settlement 200 response shape); `respond_402` — drop-in 402 emit that preserves pympp's `WWW-Authenticate` and layers x402's `PAYMENT-REQUIRED`. `build_validation_error` — structured 4xx body builder (`{error: {code, message}, required_fields?, example_body?, next_steps?, ...extra}`) so vendors compose body shapes by name instead of inlining at every validation site. |
 | `agentscore_commerce.stripe_multichain` | `create_multichain_payment_intent`, `get_deposit_address`, `simulate_crypto_deposit`; `create_pi_cache` (TTL'd PI / deposit-address cache, Redis-backed when `redis_url` set, in-memory otherwise), `simulate_deposit_if_test_mode` (gates on `sk_test_` and looks up the PI for you), `STRIPE_TEST_TX_HASH_SUCCESS` / `STRIPE_TEST_TX_HASH_FAILED` constants. Peer dep on `stripe`. |
 | `agentscore_commerce.api` | Everything from `agentscore-py` re-exported in one place: `AgentScore` + `AgentScoreError`, `AGENTSCORE_TEST_ADDRESSES` + `is_agentscore_test_address`. **Don't add `agentscore-py` as a separate dep** — the two can drift versions and cause subtle type mismatches. |