Method fetch

go/engine/node/webfetch.go:113–162

fetch validates the URL, applies SSRF pre-checks, performs the GET, reads up to webFetchMaxBytes, extracts text from HTML payloads, and truncates the result to maxChars.

(ctx context.Context, rawURL string, maxChars int)

		return "", fmt.Errorf("web_fetch %s: url: %w", n.ID(), err)
	}
	text, err := n.webFetch(ctx, webFetchArgs{URL: urlStr})
	if err != nil {
		return "", err
	}
	if err := engine.ApplyOutput(scope, n.ID(), webFetchOutID, n.binding, expr.StringVal(text)); err != nil {
		return "", fmt.Errorf("web_fetch %s: applying output: %w", n.ID(), err)
	}
	return n.Next(engine.PortCtrl, scope)
}

// webFetchArgs is the tool-call payload. A URL is always a string, so the
// schema is derivable from this type.
type webFetchArgs struct {
	URL string `json:"url"`
}

// Tools exposes this node as `web_fetch(url)`. maxChars is not a parameter —
// the author's cap applies to model-issued fetches too.
func (n *WebFetch) Tools() ([]llmproxy.FunctionTool, error) {
	ft, err := llmproxy.NewFunctionTool("web_fetch", n.toolDescription, n.webFetch)
	if err != nil {
		return nil, fmt.Errorf("web_fetch %s: %w", n.ID(), err)
	}
	return []llmproxy.FunctionTool{ft}, nil
}

// webFetch is the actual implementation of the tool call, unwrapped from the
// node execution signature.
func (n *WebFetch) webFetch(ctx context.Context, args webFetchArgs) (string, error) {
	text, err := n.fetch(ctx, args.URL, n.maxChars)
	if err != nil {
		return "", fmt.Errorf("web_fetch %s: %w", n.ID(), err)
	}
	return text, nil
}

// fetch validates the URL, applies SSRF pre-checks, performs the GET, reads up
// to webFetchMaxBytes, extracts text from HTML payloads, and truncates the
// result to maxChars.
func (n *WebFetch) fetch(ctx context.Context, rawURL string, maxChars int) (string, error) {
	parsed, err := url.Parse(strings.TrimSpace(rawURL))
	if err != nil {
		return "", fmt.Errorf("invalid url: %w", err)
	}
	if parsed.Scheme != "http" && parsed.Scheme != "https" {
		return "", fmt.Errorf("only http/https urls allowed, got %q", parsed.Scheme)
	}
	if parsed.Host == "" {
		return "", fmt.Errorf("missing host in url")
	}
	if isObviousPrivateHost(parsed.Hostname()) {
		return "", fmt.Errorf("fetching private or local hosts is not allowed")
	}