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[mcp-client] Re-inject errors into the LLM #1511

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Merged
julien-c merged 2 commits into from
Jun 16, 2025
Merged

[mcp-client] Re-inject errors into the LLM #1511

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bbcc13f
Re-inject errors into the LLM
julien-c Jun 2, 2025
55acdf1
Update packages/mcp-client/src/McpClient.ts
julien-c Jun 3, 2025
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21 changes: 17 additions & 4 deletions packages/mcp-client/src/McpClient.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -181,8 +181,6 @@ export class McpClient {
for (const toolCall of Object.values(finalToolCalls)) {
const toolName = toolCall.function.name ?? "unknown";
/// TODO(Fix upstream type so this is always a string)^
const toolArgs = toolCall.function.arguments === "" ? {} : JSON.parse(toolCall.function.arguments);

const toolMessage: ChatCompletionInputMessageTool = {
role: "tool",
tool_call_id: toolCall.id,
Expand All @@ -193,11 +191,26 @@ export class McpClient {
messages.push(toolMessage);
return yield toolMessage;
}
let toolArgs: Record<string, unknown> = {};
try {
toolArgs = toolCall.function.arguments === "" ? {} : JSON.parse(toolCall.function.arguments);
} catch (error) {
if (error instanceof SyntaxError) {
toolMessage.content = `Invalid JSON generated by the model: ${error.message}`;
} else {
throw error;
}
}

/// Get the appropriate session for this tool
const client = this.clients.get(toolName);
if (client) {
const result = await client.callTool({ name: toolName, arguments: toolArgs, signal: opts.abortSignal });
toolMessage.content = ResultFormatter.format(result);
try {
const result = await client.callTool({ name: toolName, arguments: toolArgs, signal: opts.abortSignal });
toolMessage.content = ResultFormatter.format(result);
} catch (error) {
toolMessage.content = `Error: MCP tool call failed with error message: ${error}`;
}
} else {
toolMessage.content = `Error: No session found for tool: ${toolName}`;
}
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