feat(adapters): PR_BODY.md

Author: kwailapt

adapters/python/pr-content/langchain/PR_BODY.md

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+# Add AgentCard v1.0 integration for agent identity declaration
+
+## Summary
+
+This PR adds a `langchain_community/utilities/agentcard.py` integration that allows
+LangChain tools and agents to declare their identity using the **AgentCard v1.0**
+open standard (https://github.com/kwailapt/AgentCard).
+
+AgentCard is to A2A (agent-to-agent) communication what HTTP headers are to the web:
+a standardised, machine-parseable capability declaration that works with any framework.
+
+## Why this matters
+
+As LangChain agents begin communicating with agents from other frameworks (CrewAI,
+AutoGen, custom agents), they need a **framework-neutral identity format**.
+AgentCard fills this gap:
+
+- **Zero dependencies** in core — pure Python dataclasses
+- **Framework-agnostic** — same JSON schema works for LangChain, CrewAI, AutoGen, MCP
+- **Physics-grounded pricing** — `base_cost_joules` uses Landauer's thermodynamic floor
+  as a machine-verifiable minimum cost, preventing fake "zero-cost" claims
+- **Open standard** — Apache 2.0 + CC-BY 4.0, patent non-reservation
+
+## What's included
+
+### `langchain_community/utilities/agentcard.py`
+
+- `tool_to_agentcard(tool, agent_id, endpoint_url)` — convert a `BaseTool` to AgentCard
+- `tools_to_agentcard(tools, agent_id, agent_name, endpoint_url)` — bundle multiple tools
+- `agentcard_to_tool(card)` — reconstruct a `StructuredTool` from an AgentCard
+- `AgentCardMixin` — wrap any `AgentExecutor` with AgentCard identity
+
+### `tests/unit_tests/utilities/test_agentcard.py`
+
+Full test coverage using mock tools (no network calls, no external dependencies).
+
+## Usage example
+
+```python
+from langchain.tools import BaseTool
+from langchain_community.utilities.agentcard import tool_to_agentcard
+
+class WebSearchTool(BaseTool):
+    name = "web_search"
+    description = "Search the web for current information."
+    def _run(self, query: str) -> str: ...
+
+card = tool_to_agentcard(
+    tool=WebSearchTool(),
+    agent_id="01HZQK3P8EMXR9V7T5N2W4J6C0",  # ULID
+    endpoint_url="https://my-agent.example.com/api",
+)
+print(card.to_json(indent=2))
+# {
+#   "agent_id": "01HZQK3P8EMXR9V7T5N2W4J6C0",
+#   "name": "web_search",
+#   "version": "1.0.0",
+#   "capabilities": [{"id": "web_search", "description": "Search the web..."}],
+#   "endpoint": {"protocol": "http", "url": "https://my-agent.example.com/api"}
+# }
+```
+
+## AgentCard JSON Schema
+
+Full schema: https://github.com/kwailapt/AgentCard/blob/main/schema.json
+
+Key fields:
+| Field | Type | Description |
+|-------|------|-------------|
+| `agent_id` | string | 26-char Crockford Base32 ULID |
+| `name` | string | Display name 1–128 chars |
+| `version` | string | Semantic version (semver 2.0) |
+| `capabilities[]` | array | Dot-namespaced capability ids |
+| `endpoint` | object | Protocol + URL + optional auth |
+| `pricing.base_cost_joules` | float | Landauer thermodynamic floor |
+
+## Checklist
+
+- [x] Zero new mandatory dependencies (optional: `agentcard-adapters`)
+- [x] Tests pass with mock objects (no real framework calls)
+- [x] `BaseTool.args_schema` → `input_schema` (Pydantic v1 + v2 both supported)
+- [x] Round-trip serialisation verified (Python dict ↔ JSON ↔ AgentCard)
+- [x] Landauer floor validation (physically implausible prices rejected)
+- [x] Apache 2.0 license compatible with LangChain MIT license
+
+## References
+
+- AgentCard spec: https://github.com/kwailapt/AgentCard
+- JSON Schema: https://github.com/kwailapt/AgentCard/blob/main/schema.json
+- License: Apache 2.0 + CC-BY 4.0, no patent reservation