diff --git a/mcp/README.md b/mcp/README.md
index 905acdfdb..ccc87ac45 100644
--- a/mcp/README.md
+++ b/mcp/README.md
@@ -31,9 +31,11 @@ By default the server listens on port `8085` and serves MCP over Streamable HTTP
 | Tool | Description |
 | --- | --- |
 | `search` | Perform a global search against the OpenIsle backend. |
+| `reply_to_post` | Create a new comment on a post using a JWT token. |
 | `reply_to_comment` | Reply to an existing comment using a JWT token. |
 | `recent_posts` | Retrieve posts created within the last *N* minutes. |
 
 The tools return structured data mirroring the backend DTOs, including highlighted snippets for
-search results, the full comment payload for replies, and detailed metadata for recent posts.
+search results, the full comment payload for post replies and comment replies, and detailed
+metadata for recent posts.
 
diff --git a/mcp/src/openisle_mcp/schemas.py b/mcp/src/openisle_mcp/schemas.py
index 941f13983..720c2b9db 100644
--- a/mcp/src/openisle_mcp/schemas.py
+++ b/mcp/src/openisle_mcp/schemas.py
@@ -177,6 +177,12 @@ class CommentReplyResult(BaseModel):
     comment: CommentData = Field(description="Reply comment returned by the backend.")
 
 
+class CommentCreateResult(BaseModel):
+    """Structured response returned when creating a comment on a post."""
+
+    comment: CommentData = Field(description="Comment returned by the backend.")
+
+
 class PostSummary(BaseModel):
     """Summary information for a post."""
 
diff --git a/mcp/src/openisle_mcp/search_client.py b/mcp/src/openisle_mcp/search_client.py
index 797d3f1f8..3e061211c 100644
--- a/mcp/src/openisle_mcp/search_client.py
+++ b/mcp/src/openisle_mcp/search_client.py
@@ -66,6 +66,35 @@ class SearchClient:
         response.raise_for_status()
         return self._ensure_dict(response.json())
 
+    async def reply_to_post(
+        self,
+        post_id: int,
+        token: str,
+        content: str,
+        captcha: str | None = None,
+    ) -> dict[str, Any]:
+        """Create a comment on a post and return the backend payload."""
+
+        client = self._get_client()
+        headers = {
+            "Accept": "application/json",
+            "Content-Type": "application/json",
+            "Authorization": f"Bearer {token}",
+        }
+        payload: dict[str, Any] = {"content": content}
+        if captcha is not None:
+            stripped_captcha = captcha.strip()
+            if stripped_captcha:
+                payload["captcha"] = stripped_captcha
+
+        response = await client.post(
+            f"/api/posts/{post_id}/comments",
+            json=payload,
+            headers=headers,
+        )
+        response.raise_for_status()
+        return self._ensure_dict(response.json())
+
     async def recent_posts(self, minutes: int) -> list[dict[str, Any]]:
         """Return posts created within the given timeframe."""
 
diff --git a/mcp/src/openisle_mcp/server.py b/mcp/src/openisle_mcp/server.py
index 094c815a8..9f5a6af31 100644
--- a/mcp/src/openisle_mcp/server.py
+++ b/mcp/src/openisle_mcp/server.py
@@ -12,6 +12,7 @@ from pydantic import Field as PydanticField
 
 from .config import get_settings
 from .schemas import (
+    CommentCreateResult,
     CommentData,
     CommentReplyResult,
     PostDetail,
@@ -41,9 +42,9 @@ async def lifespan(_: FastMCP):
 app = FastMCP(
     name="openisle-mcp",
     instructions=(
-        "Use this server to search OpenIsle content, reply to comments with an authentication "
-        "token, retrieve details for a specific post, and list posts created within a recent time "
-        "window."
+        "Use this server to search OpenIsle content, reply to posts and comments with an "
+        "authentication token, retrieve details for a specific post, and list posts created "
+        "within a recent time window."
     ),
     host=settings.host,
     port=settings.port,
@@ -96,6 +97,100 @@ async def search(
     return SearchResponse(keyword=sanitized, total=len(results), results=results)
 
 
+@app.tool(
+    name="reply_to_post",
+    description="Create a comment on a post using an authentication token.",
+    structured_output=True,
+)
+async def reply_to_post(
+    post_id: Annotated[
+        int,
+        PydanticField(ge=1, description="Identifier of the post being replied to."),
+    ],
+    token: Annotated[
+        str,
+        PydanticField(description="JWT bearer token for the user performing the reply."),
+    ],
+    content: Annotated[
+        str,
+        PydanticField(description="Markdown content of the reply."),
+    ],
+    captcha: Annotated[
+        str | None,
+        PydanticField(
+            default=None,
+            description="Optional captcha solution if the backend requires it.",
+        ),
+    ] = None,
+    ctx: Context | None = None,
+) -> CommentCreateResult:
+    """Create a comment on a post and return the backend payload."""
+
+    sanitized_content = content.strip()
+    if not sanitized_content:
+        raise ValueError("Reply content must not be empty.")
+
+    sanitized_token = token.strip()
+    if not sanitized_token:
+        raise ValueError("Authentication token must not be empty.")
+
+    sanitized_captcha = captcha.strip() if isinstance(captcha, str) else None
+
+    try:
+        raw_comment = await search_client.reply_to_post(
+            post_id,
+            sanitized_token,
+            sanitized_content,
+            sanitized_captcha,
+        )
+    except httpx.HTTPStatusError as exc:  # pragma: no cover - network errors
+        status_code = exc.response.status_code
+        if status_code == 401:
+            message = (
+                "Authentication failed while replying to post "
+                f"{post_id}. Please verify the token."
+            )
+        elif status_code == 403:
+            message = (
+                "The provided token is not authorized to reply to post "
+                f"{post_id}."
+            )
+        elif status_code == 404:
+            message = f"Post {post_id} was not found."
+        else:
+            message = (
+                "OpenIsle backend returned HTTP "
+                f"{status_code} while replying to post {post_id}."
+            )
+        if ctx is not None:
+            await ctx.error(message)
+        raise ValueError(message) from exc
+    except httpx.RequestError as exc:  # pragma: no cover - network errors
+        message = (
+            "Unable to reach OpenIsle backend comment service: "
+            f"{exc}."
+        )
+        if ctx is not None:
+            await ctx.error(message)
+        raise ValueError(message) from exc
+
+    try:
+        comment = CommentData.model_validate(raw_comment)
+    except ValidationError as exc:
+        message = "Received malformed data from the post comment endpoint."
+        if ctx is not None:
+            await ctx.error(message)
+        raise ValueError(message) from exc
+
+    if ctx is not None:
+        await ctx.info(
+            "Reply created successfully for post "
+            f"{post_id}."
+        )
+
+    return CommentCreateResult(comment=comment)
+
+
 @app.tool(
     name="reply_to_comment",
     description="Reply to an existing comment using an authentication token.",