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Fix: Non-existent tool, disabled tool and inputSchema validation return MCP protocol level instead of CallToolResult with isError: true #1044

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Merged
merged 6 commits into from
Oct 28, 2025
+150 −116
Merged

Fix: Non-existent tool, disabled tool and inputSchema validation return MCP protocol level instead of CallToolResult with isError: true #1044

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efd901a
Non-existing tool, disabled tool and tool inputSchema validation retu…
KKonstantinov Oct 24, 2025
8705e69
Merge branch 'main' into bugfix/tool-validation-not-jsonrpc-error
KKonstantinov Oct 25, 2025
a0fce2a
Merge branch 'main' into bugfix/tool-validation-not-jsonrpc-error
KKonstantinov Oct 28, 2025
2cc4918
Merge branch 'main' into bugfix/tool-validation-not-jsonrpc-error
KKonstantinov Oct 28, 2025
f02ff1a
outputSchema fix - return CallToolResult on structuredContent not ret…
KKonstantinov Oct 28, 2025
98a69ba
prettier fix
KKonstantinov Oct 28, 2025
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96 changes: 60 additions & 36 deletions src/server/mcp.test.ts
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -928,37 +928,53 @@ describe('tool()', () => {

await Promise.all([client.connect(clientTransport), mcpServer.server.connect(serverTransport)]);

await expect(
client.request(
{
method: 'tools/call',
params: {
const result = await client.request(
{
method: 'tools/call',
params: {
name: 'test',
arguments: {
name: 'test',
arguments: {
name: 'test',
value: 'not a number'
}
value: 'not a number'
}
},
CallToolResultSchema
)
).rejects.toThrow(/Invalid arguments/);
}
},
CallToolResultSchema
);

await expect(
client.request(
expect(result.isError).toBe(true);
expect(result.content).toEqual(
expect.arrayContaining([
{
method: 'tools/call',
params: {
name: 'test (new api)',
arguments: {
name: 'test',
value: 'not a number'
}
type: 'text',
text: expect.stringContaining('Invalid arguments')
}
])
);

const result2 = await client.request(
{
method: 'tools/call',
params: {
name: 'test (new api)',
arguments: {
name: 'test',
value: 'not a number'
}
},
CallToolResultSchema
)
).rejects.toThrow(/Invalid arguments/);
}
},
CallToolResultSchema
);

expect(result2.isError).toBe(true);
expect(result2.content).toEqual(
expect.arrayContaining([
{
type: 'text',
text: expect.stringContaining('Invalid arguments')
}
])
);
});

/***
Expand Down Expand Up @@ -1552,17 +1568,25 @@ describe('tool()', () => {

await Promise.all([client.connect(clientTransport), mcpServer.server.connect(serverTransport)]);

await expect(
client.request(
const result = await client.request(
{
method: 'tools/call',
params: {
name: 'nonexistent-tool'
}
},
CallToolResultSchema
);

expect(result.isError).toBe(true);
expect(result.content).toEqual(
expect.arrayContaining([
{
method: 'tools/call',
params: {
name: 'nonexistent-tool'
}
},
CallToolResultSchema
)
).rejects.toThrow(/Tool nonexistent-tool not found/);
type: 'text',
text: expect.stringContaining('Tool nonexistent-tool not found')
}
])
);
});

/***
Expand Down
82 changes: 41 additions & 41 deletions src/server/mcp.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -126,55 +126,37 @@ export class McpServer {

this.server.setRequestHandler(CallToolRequestSchema, async (request, extra): Promise<CallToolResult> => {
const tool = this._registeredTools[request.params.name];
if (!tool) {
throw new McpError(ErrorCode.InvalidParams, `Tool ${request.params.name} not found`);
}

if (!tool.enabled) {
throw new McpError(ErrorCode.InvalidParams, `Tool ${request.params.name} disabled`);
}

let result: CallToolResult;

if (tool.inputSchema) {
const parseResult = await tool.inputSchema.safeParseAsync(request.params.arguments);
if (!parseResult.success) {
throw new McpError(
ErrorCode.InvalidParams,
`Invalid arguments for tool ${request.params.name}: ${parseResult.error.message}`
);
try {
if (!tool) {
throw new McpError(ErrorCode.InvalidParams, `Tool ${request.params.name} not found`);
}

const args = parseResult.data;
const cb = tool.callback as ToolCallback<ZodRawShape>;
try {
result = await Promise.resolve(cb(args, extra));
} catch (error) {
result = {
content: [
{
type: 'text',
text: error instanceof Error ? error.message : String(error)
}
],
isError: true
};
if (!tool.enabled) {
throw new McpError(ErrorCode.InvalidParams, `Tool ${request.params.name} disabled`);
}
} else {
const cb = tool.callback as ToolCallback<undefined>;
try {

if (tool.inputSchema) {
const cb = tool.callback as ToolCallback<ZodRawShape>;
const parseResult = await tool.inputSchema.safeParseAsync(request.params.arguments);
if (!parseResult.success) {
throw new McpError(
ErrorCode.InvalidParams,
`Invalid arguments for tool ${request.params.name}: ${parseResult.error.message}`
);
}

const args = parseResult.data;

result = await Promise.resolve(cb(args, extra));
} else {
const cb = tool.callback as ToolCallback<undefined>;
result = await Promise.resolve(cb(extra));
} catch (error) {
result = {
content: [
{
type: 'text',
text: error instanceof Error ? error.message : String(error)
}
],
isError: true
};
}
} catch (error) {
return this.createToolError(error instanceof Error ? error.message : String(error));
}

if (tool.outputSchema && !result.isError) {
Expand All @@ -201,6 +183,24 @@ export class McpServer {
this._toolHandlersInitialized = true;
}

/**
* Creates a tool error result.
*
* @param errorMessage - The error message.
* @returns The tool error result.
*/
private createToolError(errorMessage: string): CallToolResult {
return {
content: [
{
type: 'text',
text: errorMessage
}
],
isError: true
};
}

private _completionHandlerInitialized = false;

private setCompletionRequestHandler() {
Expand Down