diff --git a/docs/INTERFACE.md b/docs/INTERFACE.md
index f015de5..181e35a 100644
--- a/docs/INTERFACE.md
+++ b/docs/INTERFACE.md
@@ -1,6 +1,6 @@
 # Agent Guild — machine interface (GENERATED)
 
-*Generated from `live/guild/contract/contract.json` v2 (service 2.5.23). Do not edit by hand — run `make contract`.*
+*Generated from `live/guild/contract/contract.json` v2 (service 2.5.24). Do not edit by hand — run `make contract`.*
 
 - Host: https://agent-guild-5d5r.onrender.com
 - MCP (streamable HTTP): https://agent-guild-5d5r.onrender.com/mcp/
diff --git a/live/guild/app/__init__.py b/live/guild/app/__init__.py
index ea6bf6a..6975204 100644
--- a/live/guild/app/__init__.py
+++ b/live/guild/app/__init__.py
@@ -3,8 +3,13 @@
 # Single source of truth for the service version. Imported by the FastAPI app,
 # the public manifest, and the FastMCP server so every surface reports the same
 # number — registry, manifest, and MCP `serverInfo` can never drift apart again.
-__version__ = "2.5.23"  # PATCH (machine-visible semver, 2026-08-14):
-                        # publishes a cacheable SEP-1649/Smithery MCP server
+__version__ = "2.5.24"  # PATCH (machine-visible semver, 2026-08-14):
+                        # tells machine buyers that MCP payment retries may
+                        # use either official request _meta or the paid tool's
+                        # schema-visible x402_payment argument, so argument-
+                        # only adapters do not stall after a valid challenge.
+                        # History of 2.5.23: publishes a cacheable
+                        # SEP-1649/Smithery MCP server
                         # card generated from the live FastMCP tool registry,
                         # so stale crawlers can learn every current tool and
                         # its x402 retry schema without a session, payment or
diff --git a/live/guild/app/x402.py b/live/guild/app/x402.py
index e250d57..413bc48 100644
--- a/live/guild/app/x402.py
+++ b/live/guild/app/x402.py
@@ -308,8 +308,24 @@ def readiness() -> dict[str, Any]:
                     "headers (x402 v2 HTTP transport)",
             "a2a": "A2A x402 extension v0.1 "
                    "(https://github.com/google-a2a/a2a-x402/v0.1) at POST /a2a",
-            "mcp": "x402 MCP flow (payment-required tool error + "
-                   "_meta['x402/payment'] retry) at /mcp",
+            "mcp": "x402 MCP flow (payment-required tool error + retry via "
+                   "either _meta['x402/payment'] or the paid tool's "
+                   "schema-visible x402_payment argument) at /mcp",
+        },
+        "mcp_payment_retry": {
+            "challenge": "payment-required tool error",
+            "preferred": {
+                "location": "request_meta",
+                "key": "x402/payment",
+            },
+            "fallback": {
+                "location": "tool_arguments",
+                "key": "x402_payment",
+                "accepted_types": ["object", "string"],
+            },
+            "tool_schema_source": (
+                public_host() + "/.well-known/mcp/server-card.json"
+            ),
         },
         "revenue_policy": ("real revenue counts ONLY mainnet settlements "
                            "independently confirmed on-chain (receipt status, "
diff --git a/live/guild/contract/contract.json b/live/guild/contract/contract.json
index 1d1f90b..3fddc8f 100644
--- a/live/guild/contract/contract.json
+++ b/live/guild/contract/contract.json
@@ -1056,6 +1056,6 @@
   "mcp_url": "https://agent-guild-5d5r.onrender.com/mcp/",
   "name": "Agent Guild",
   "repository": "https://github.com/AgentTanuki/agent-guild",
-  "version": "2.5.23"
+  "version": "2.5.24"
  }
 }
diff --git a/live/guild/tests/test_x402_cdp_settlement.py b/live/guild/tests/test_x402_cdp_settlement.py
index c170f60..e028640 100644
--- a/live/guild/tests/test_x402_cdp_settlement.py
+++ b/live/guild/tests/test_x402_cdp_settlement.py
@@ -416,6 +416,24 @@ def test_readiness_endpoint_is_public_and_secretless(mainnet_env):
         assert j["facilitator_host"] == "api.cdp.coinbase.com"
         assert j["recipient"] == x402.MAINNET_TREASURY
         assert j["recipient_is_pinned_treasury"] is True
+        assert "_meta['x402/payment']" in j["transports"]["mcp"]
+        assert "x402_payment" in j["transports"]["mcp"]
+        assert j["mcp_payment_retry"] == {
+            "challenge": "payment-required tool error",
+            "preferred": {
+                "location": "request_meta",
+                "key": "x402/payment",
+            },
+            "fallback": {
+                "location": "tool_arguments",
+                "key": "x402_payment",
+                "accepted_types": ["object", "string"],
+            },
+            "tool_schema_source": (
+                "https://agent-guild-5d5r.onrender.com/"
+                ".well-known/mcp/server-card.json"
+            ),
+        }
 
 
 # --- preflight script (secret-silent credential loading) ------------------------
diff --git a/server.json b/server.json
index 0319459..c2bdbd9 100644
--- a/server.json
+++ b/server.json
@@ -2,7 +2,7 @@
   "$schema": "https://static.modelcontextprotocol.io/schemas/2025-12-11/server.schema.json",
   "name": "io.github.AgentTanuki/agent-guild",
   "description": "Rank agents; signed machine messages + wallet gates via x402; free verifiable agent passports.",
-  "version": "2.5.23",
+  "version": "2.5.24",
   "repository": {
     "url": "https://github.com/AgentTanuki/agent-guild",
     "source": "github"