A client for a remote MCP server

Made by mcp_client(). The methods below block until the server answers and raise an error of class shinymcp_error_client when it reports one. Each has an _async variant that returns a promise instead, for use in Shiny.

Public fields

url

The server's endpoint.

name

The name hosts know the server by.

timeout

Seconds to wait for each response.

Methods

Public methods

• McpClient$new()

• McpClient$tools()

• McpClient$call_tool()

• McpClient$read_resource()

• McpClient$request()

• McpClient$send()

• McpClient$tools_async()

• McpClient$call_tool_async()

• McpClient$read_resource_async()

• McpClient$request_async()

• McpClient$send_async()

• McpClient$protocol_version()

• McpClient$server_info()

• McpClient$close()

• McpClient$print()

---

McpClient$new()

Create a client. Use mcp_client().

Usage

McpClient$new(url, headers = NULL, name = NULL, timeout = 60, transport = NULL)

Arguments

url, headers, name, timeout

See mcp_client().

transport

For tests: a function taking a request (a list with method, url, headers, body, and the JSON-RPC id), async, and timeout, and returning a response (status, headers, body) or a promise of one.

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McpClient$tools()

The server's tools, from tools/list, with their _meta. The list is kept for as long as the server says it may be, or a minute.

Usage

McpClient$tools(refresh = FALSE, wait = TRUE)

Arguments

refresh

Read the list again even if it is kept.

wait

FALSE to return the last list the client got, however old, without asking the server: NULL if it has none.

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McpClient$call_tool()

Call a tool.

Usage

McpClient$call_tool(name, arguments = NULL)

Arguments

name

Tool name.

arguments

Named list of arguments, sent as JSON. A vector of one value goes as one value; write an array of one as list(x).

Returns

The tools/call result: a list with content, and possibly structuredContent, _meta, and isError.

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McpClient$read_resource()

Read a resource, such as an app's ui:// page.

Usage

McpClient$read_resource(uri)

Arguments

uri

Resource URI.

Returns

The resources/read result, a list with contents.

---

McpClient$request()

Send any request and return its result.

Usage

McpClient$request(method, params = NULL)

Arguments

method

JSON-RPC method.

params

Named list of parameters.

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McpClient$send()

Send a JSON-RPC request and return the whole response, errors included, with the request's own id. Hosts use this to pass an app's requests on.

Usage

McpClient$send(message)

Arguments

message

A JSON-RPC request (a list).

---

McpClient$tools_async()

tools(), returning a promise.

Usage

McpClient$tools_async(refresh = FALSE)

Arguments

refresh

Read the list again even if it is kept.

---

McpClient$call_tool_async()

call_tool(), returning a promise.

Usage

McpClient$call_tool_async(name, arguments = NULL)

Arguments

name

Tool name.

arguments

Named list of arguments.

---

McpClient$read_resource_async()

read_resource(), returning a promise.

Usage

McpClient$read_resource_async(uri)

Arguments

uri

Resource URI.

---

McpClient$request_async()

request(), returning a promise.

Usage

McpClient$request_async(method, params = NULL)

Arguments

method

JSON-RPC method.

params

Named list of parameters.

---

McpClient$send_async()

send(), returning a promise.

Usage

McpClient$send_async(message)

Arguments

message

A JSON-RPC request (a list).

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McpClient$protocol_version()

The protocol version in use, or NULL before the first request.

Usage

McpClient$protocol_version()

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McpClient$server_info()

What the server said about itself (name, version), or NULL before the first request.

Usage

McpClient$server_info()

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McpClient$close()

End the session, for servers that keep one. The next request starts a new one.

Usage

McpClient$close()

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McpClient$print()

Print a summary.

Usage

McpClient$print(...)

Arguments

...

Ignored.