affaan-m/ECC · error · MCPException

Invalid name provided

Error message

Invalid name provided

What it means

Illustrative input-sanitization guard in a tinystruct MCP tool example: the tool validates its `name` argument before returning it to the model and throws on an invalid value. The unvalidated tool input (the name parameter) is the faulty input; the comment marks this as a prompt-injection defense.

Source

Thrown at skills/tinystruct-patterns/SKILL.md:170

import org.tinystruct.system.annotation.Argument;

public class MyCustomTool extends MCPTool {
    public MyCustomTool() {
        super("custom", "A custom tool for demonstrating MCP");
    }

    @Action(
        value = "custom/hello",
        description = "Say hello to someone",
        arguments = {
            @Argument(key = "name", description = "The name to greet", type = "string", optional = false)
        }
    )
    public String hello(String name) throws MCPException {
        // SECURITY: Validate/sanitize tool inputs before returning to the model
        // to prevent prompt injection vulnerabilities.
        if (name == null || name.length() > 50 || !name.matches("^[a-zA-Z0-9 ]+$")) {
            throw new MCPException("Invalid name provided");
        }
        return "Hello, " + name + "!";
    }
}
```

**To deploy an MCP Server:**
1. Extend `org.tinystruct.mcp.MCPServer`.
2. Override `init()` and register your tools using `this.registerTool()`. The framework automatically scans and maps the `@Action` methods.

```java
import org.tinystruct.mcp.MCPServer;

public class MyMCPServer extends MCPServer {
    @Override
    public void init() {
        super.init();
        this.registerTool(new MyCustomTool());

View on GitHub (pinned to d8409a4b08)

Solutions

1. Apply schema validation (length, charset) to every tool argument
2. Escape or strip control characters before echoing input back to the model
3. Return a structured validation error the MCP client can display

When it happens

Trigger: Thrown at skills/tinystruct-patterns/SKILL.md:170 when the library encounters an invalid state.

Common situations: See trigger scenarios.

AI-assisted analysis of affaan-m/ECC@d8409a4b08 (2026-08-26). Data as JSON: /api/errors/3855db415218bed6. Report an issue: GitHub.