McpServer class using an outputSchema gobbles thrown errors from tool calls

[jsas]

When a tool is registered with an output schema using the McpServer class , errors thrown in the tool call are not considered in the response logic and will throw another error: MCP error -32602: MCP error -32602: Tool ${toolName} has an output schema but no structured content was provided

Steps to reproduce the behavior:

1. register a tool with an outputSchema.
2. throw an error in the tool call.
3. observe the error is swallowed by the output logic.

I expect the error I threw to be thrown. Same if I choose to return a content error ({ content: ..., isError: true })

Maybe if (tool.outputSchema && !result?.isError) { on that line?

[sergii-kamenskyi]

@jsas seems to be fixed in the latest version. I tested it with 1.15.0. If you let the tool throw errors. Framework automatically catches and converts to message format with {isError: true,...}
see

typescript-sdk/src/server/mcp.ts

Line 203 in 1ac2e59

if (tool.outputSchema && !result.isError) {

[slhad]

Just after the line mentioned by @sergii-kamenskyi , you can see

typescript-sdk/src/server/mcp.ts

Line 204 in 1ac2e59

if (!result.structuredContent) {

)

Which is not documented but needed when using outputSchema, I would also have loved to see that a lot sooner