Received error: Swift.DecodingError.dataCorrupted

[jamesrochabrun]

Some tools responses are not in the expected format and Decoding fails.

Repro

On this repro you can see that using the list_issues will not repro the decoding issue, but if we use list_commits instead we encounter this decoding error, I think the data is coming with some escaped strings that are making this decoding failure.

Received data:
: \"42123b0b64f3ea0b4ea820ea2db8df4b7fef6ea5\",\n        \"url\": \"https://api.github.com/repos/jamesrochabrun/SwiftAnthropic/git/trees/42123b0b64f3ea0b4ea820ea2db8df4b7fef6ea5\"\n      },\n      \"url\": \"https://api.github.com/repos/jamesrochabrun/SwiftAnthropic/git/commits/7424471d5a85dc088137d22dcc5a5903d62864a1\",\n      \"comment_count\": 0,\n      \"verification\": {\n        \"verified\": false,\n        \"reason\": \"unsigned\",\n        \"signature\": null,\n        \"payload\": null,\n        \"verified_at\": null\n      }\n    },\n    \"url\": \"https://api.github.com/repos/jamesrochabrun/SwiftAnthropic/commits/7424471d5a85dc088137d22dcc5a5903d62864a1\",\n    \"html_url\": \"https://github.com/jamesrochabrun/SwiftAnthropic/commit/7424471d5a85dc088137d22dcc5a5903d62864a1\",\n    \"comments_url\": \"https://api.github.com/repos/jamesrochabrun/SwiftAnthropic/commits/7424471d5a85dc088137d22dcc5a5903d62864a1/comments\",\n    \"author\": null,\n    \"committer\": null,\n    \"parents\": [\n      {\n        \"sha\": \"a624abcf464117a0c113043d0b94f294b4bed4d1\",\n        \"url\": \"https://api.github.com/repos/jamesrochabrun/SwiftAnthropic/commits/a624abcf464117a0c113043d0b94f294b4bed4d1\",\n        \"html_url\": \"https://github.com/jamesrochabrun/SwiftAnthropic/commit/a624abcf464117a0c113043d0b94f294b4bed4d1\"\n      }\n    ]\n  }\n]"}]},"jsonrpc":"2.0","id":3}

I believe the decoding failure comes from this function in the JSONRPC package

	public func sendRequest<Request, Response>(_ params: Request, method: String) async throws -> JSONRPCResponse<Response>
	where Request: Encodable, Response: Decodable {
		let (_, data) = try await sendDataRequest(params, method: method)

		return try decoder.decode(JSONRPCResponse<Response>.self, from: data)
	}

Repro code

let client = try await MCPClient(
  info: .init(name: "test", version: "1.0.0"),
  transport: .stdioProcess(
    "npx",
    args: ["-y", "@modelcontextprotocol/server-github"],
    verbose: true),
  capabilities: .init())

let tools = await client.tools
let tool = try tools.value.get().first(where: { $0.name == "list_issues" })! // change this tool for `list_commits` to see erro
print("tool: \(tool)")

// Those parameters can be passed to an LLM that support tool calling.
let description = tool.description
let name = tool.name
let schemaData = try JSONEncoder().encode(tool.inputSchema)
let schema = try JSONSerialization.jsonObject(with: schemaData)

/// The LLM could call into the tool with unstructured JSON input:
let llmToolInput: [String: Any] = [
  "repo": "SwiftAnthropic",
  "owner": "jamesrochabrun"
]
let llmToolInputData = try JSONSerialization.data(withJSONObject: llmToolInput)
let toolInput = try JSONDecoder().decode(JSON.self, from: llmToolInputData)

let result = try await client.callTool(named: name, arguments: toolInput)
if result.isError != true {
  let content = result.content.first?.text?.text
  print("Git status: \(content ?? "")")
}

[gsabran]

Should be fixed by #11

The issue was that the local process would write its json data to stdio, and that data would be flushed in several parts that needed to be put together in the transport layer before being decoded as JRPC events.