continuedev/continue · error · Error

Invalid MCP tool reference "${toolRef}": colon-separated too

Error message

Invalid MCP tool reference "${toolRef}": colon-separated tool references cannot contain whitespace. Use format "https://server:tool_name" without spaces.

What it means

In parseAgentFileTools, a URL-like tool reference containing a colon was checked after the last colon; when it looks like a tool name/port but the whole reference contains whitespace, it is rejected to prevent silent misconfiguration.

Source

Thrown at packages/config-yaml/src/markdown/agentFiles.ts:145

      // Check if there's a colon after the protocol
      if (lastColonIndex > protocolEndIndex) {
        const afterLastColon = toolRef.substring(lastColonIndex + 1);

        // Check if it's a port number (only digits), empty string, or a tool name
        if (/^\d+(?:$|[/?#])/.test(afterLastColon)) {
          // It's a port number, treat the whole thing as the server
          const mcpServer = toolRef;
          tools.push({ mcpServer });
          mcpServerSet.add(mcpServer);
        } else if (
          afterLastColon === "" ||
          /^[a-zA-Z0-9_-]+$/.test(afterLastColon)
        ) {
          // It's a tool name (or empty string)
          // Reject references with whitespace to prevent silent misconfigurations
          if (/\s/.test(toolRef)) {
            throw new Error(
              `Invalid MCP tool reference "${toolRef}": colon-separated tool references cannot contain whitespace. ` +
                `Use format "https://server:tool_name" without spaces.`,
            );
          }

          const mcpServer = toolRef.substring(0, lastColonIndex);
          const toolName = afterLastColon;

          tools.push({ mcpServer, toolName });
          mcpServerSet.add(mcpServer);
        } else {
          throw new Error(
            `Invalid URL-based MCP tool reference "${toolRef}": the part after the last colon must be either a port number or a valid tool name (alphanumeric, underscores, hyphens).`,
          );
        }
      } else {
        // No colon after the protocol, treat the whole thing as the server
        const mcpServer = toolRef;

View on GitHub (pinned to 5522c6f44c)

Solutions

  1. Remove all whitespace from the URL-form tool reference
  2. Use the exact format https://server:tool_name
  3. Lint agent file tool lists for spaces

Example fix

# before
tools:
  - "https://my server:tool_name"
# after
tools:
  - "https://myserver:tool_name"
Defensive patterns

Strategy: validation

Validate before calling

const valid = toolRefs.every(r => /^\S+$/.test(r));

Type guard

function isCleanToolRef(ref: string): boolean { return !/\s/.test(ref); }

Try / catch

try { parseAgentFileTools(refs); } catch (e) { if (e.message.includes('whitespace')) { /* strip spaces and retry */ } }

Prevention

When it happens

Trigger: A tools entry like 'https://my server:tool_name' or 'https://server:my tool' — URL-form reference with any whitespace anywhere in the string.

Common situations: Copy/pasting tool references with trailing spaces or line-wrapped URLs, or YAML flow lists inserting spaces.

Related errors

AI-assisted analysis of continuedev/continue@5522c6f44c (2026-08-27). Data as JSON: /api/errors/652bb8909bb6a74c. Report an issue: GitHub.