@@ -3,30 +3,47 @@
 from dataclasses import dataclass, field
 from typing import Any
 
-DEFAULT_RECOMMENDED_TOOLS = [
-    "`tempo request` for Tempo USDC (installs via `tempo add request`)",
-    (
-        "`agentscore-pay` (npm: `@agent-score/pay`) — single CLI for x402 on Base + Solana, "
-        "also speaks tempo MPP via `--chain tempo`"
-    ),
-]
+_TEMPO_WARNING = (
+    "Do NOT use `tempo wallet transfer` to pay to the address above. That moves USDC on-chain but does not "
+    "notify this server, leaving your order in pending_identity state. Use `tempo request` instead — it performs "
+    "the full MPP handshake (signs, submits Authorization: Payment, waits for server confirmation)."
+)
+_X402_WARNING = (
+    "Do NOT send USDC manually to the x402 deposit addresses (e.g. via a bare wallet `transfer`). Use "
+    "`agentscore-pay pay` so the X-Payment credential is signed and submitted; otherwise the order stays in "
+    "pending_identity even though the deposit lands."
+)
+_TEMPO_TOOL = "`tempo request` for Tempo USDC (installs via `tempo add request`)"
+_AGENTSCORE_PAY_TOOL = (
+    "`agentscore-pay` (npm: `@agent-score/pay`) — single CLI for x402 on Base + Solana, "
+    "also speaks tempo MPP via `--chain tempo`"
+)
+
 DEFAULT_WALLET_COMPATIBILITY = (
     "No specific wallet stack required. The 402 challenge is rail-neutral: any client that can produce a valid "
     "MPP credential (Authorization: Payment) or x402 X-Payment header is accepted. The CLI commands above are "
     "the easiest path; sign-it-yourself is fine too."
 )
-DEFAULT_WARNINGS = [
-    (
-        "Do NOT use `tempo wallet transfer` to pay to the address above. That moves USDC on-chain but does not "
-        "notify this server, leaving your order in pending_identity state. Use `tempo request` instead — it performs "
-        "the full MPP handshake (signs, submits Authorization: Payment, waits for server confirmation)."
-    ),
-    (
-        "Do NOT send USDC manually to the x402 deposit addresses (e.g. via a bare wallet `transfer`). Use "
-        "`agentscore-pay pay` so the X-Payment credential is signed and submitted; otherwise the order stays in "
-        "pending_identity even though the deposit lands."
-    ),
-]
+
+
+def _default_recommended_tools(how_to_pay: dict[str, Any]) -> list[str]:
+    tools: list[str] = []
+    has_tempo = "tempo" in how_to_pay
+    has_x402 = "x402_base" in how_to_pay or "x402_solana" in how_to_pay
+    if has_tempo:
+        tools.append(_TEMPO_TOOL)
+    if has_tempo or has_x402:
+        tools.append(_AGENTSCORE_PAY_TOOL)
+    return tools
+
+
+def _default_warnings(how_to_pay: dict[str, Any]) -> list[str]:
+    w: list[str] = []
+    if "tempo" in how_to_pay:
+        w.append(_TEMPO_WARNING)
+    if "x402_base" in how_to_pay or "x402_solana" in how_to_pay:
+        w.append(_X402_WARNING)
+    return w
 
 
 @dataclass
@@ -41,13 +58,22 @@ class BuildAgentInstructionsInput:
 
 
 def build_agent_instructions(input: BuildAgentInstructionsInput) -> dict[str, Any]:
-    """Build the agent_instructions block — combines how_to_pay with tools, warnings, compat note, timeout."""
+    """Build the agent_instructions block — combines how_to_pay with tools, warnings, compat note, timeout.
+
+    Defaults adapt to the rails declared in ``how_to_pay``: only tempo-relevant warnings/tools
+    appear if ``how_to_pay["tempo"]`` is set, only x402-relevant ones if ``x402_base``/
+    ``x402_solana`` are set. Vendors override ``warnings``/``recommended_tools`` for full control.
+    """
+    recommended_tools = (
+        input.recommended_tools if input.recommended_tools is not None else _default_recommended_tools(input.how_to_pay)
+    )
+    warnings = input.warnings if input.warnings is not None else _default_warnings(input.how_to_pay)
     out: dict[str, Any] = {
         "how_to_pay": input.how_to_pay,
-        "recommended_tools": input.recommended_tools or DEFAULT_RECOMMENDED_TOOLS,
+        "recommended_tools": recommended_tools,
         "wallet_compatibility": input.wallet_compatibility or DEFAULT_WALLET_COMPATIBILITY,
         "timeout_seconds": input.timeout_seconds,
-        "warnings": input.warnings if input.warnings is not None else DEFAULT_WARNINGS,
+        "warnings": warnings,
     }
     if input.recommended:
         out["recommended"] = input.recommended
 
@@ -115,6 +115,22 @@ def test_build_agent_instructions_uses_defaults():
     assert any("tempo wallet transfer" in w for w in out["warnings"])
 
 
+def test_build_agent_instructions_warnings_match_rails():
+    """Defaults adapt to which rails are present in how_to_pay."""
+    x402_only = build_agent_instructions(BuildAgentInstructionsInput(how_to_pay={"x402_base": {}}))
+    assert not any("tempo wallet transfer" in w for w in x402_only["warnings"])
+    assert any("x402 deposit addresses" in w for w in x402_only["warnings"])
+    assert not any("tempo request" in t for t in x402_only["recommended_tools"])
+    assert any("agentscore-pay" in t for t in x402_only["recommended_tools"])
+
+    tempo_only = build_agent_instructions(BuildAgentInstructionsInput(how_to_pay={"tempo": {}}))
+    assert not any("x402 deposit addresses" in w for w in tempo_only["warnings"])
+
+    stripe_only = build_agent_instructions(BuildAgentInstructionsInput(how_to_pay={"stripe": {}}))
+    assert stripe_only["warnings"] == []
+    assert stripe_only["recommended_tools"] == []
+
+
 def test_build_402_body_assembles_full_response():
     body = build_402_body(
         Build402BodyInput(