What causes "failed to read response body: %w" in googleapis/mcp-toolbox?

Retry the request — transient body-read failures usually resolve on a second attempt

failed to read response body: %w

Error message

failed to read response body: %w

What it means

This error wraps a failure from io.ReadAll(resp.Body) in ExecuteMQL — the HTTP request succeeded and got a response, but the response body could not be fully read. This is rare and usually indicates the connection was reset or timed out mid-transfer, or the response body reader errored.

Source

Thrown at internal/sources/firestore/firestore.go:932

	req, err := http.NewRequestWithContext(ctx, http.MethodPost, url, bytes.NewReader(bodyBytes))
	if err != nil {
		return nil, fmt.Errorf("failed to create HTTP request: %w", err)
	}
	req.Header.Set("Content-Type", "application/json")
	req.Header.Set("User-Agent", userAgent)
	req.Header.Set("x-goog-request-params", fmt.Sprintf("project_id=%s&database_id=%s", s.GetProjectId(), s.GetDatabaseId()))
	req.Header.Set("x-goog-firestore-api-requester", "querydata")

	resp, err := httpClient.Do(req)
	if err != nil {
		return nil, fmt.Errorf("failed to execute pipeline request: %w", err)
	}
	defer resp.Body.Close()

	respBody, err := io.ReadAll(resp.Body)
	if err != nil {
		return nil, fmt.Errorf("failed to read response body: %w", err)
	}

	if resp.StatusCode < 200 || resp.StatusCode >= 300 {
		return nil, fmt.Errorf("executePipeline API error (status %d): %s", resp.StatusCode, string(respBody))
	}

	var result any
	if err := json.Unmarshal(respBody, &result); err != nil {
		return string(respBody), nil
	}

	return result, nil
}

func initFirestoreConnection(
	ctx context.Context,
	tracer trace.Tracer,
	name string,

View on GitHub (pinned to 8cc6e09de2)

Solutions

Retry the request — transient body-read failures usually resolve on a second attempt
Check for proxies/load balancers truncating responses and increase their timeouts
Increase the HTTP client/context timeout so large responses can finish streaming

Defensive patterns

Strategy: retry

Try / catch

res, err := src.ExecuteMQL(ctx, pipeline)
if err != nil && strings.Contains(err.Error(), "failed to read response body") {
    // transient: safe to retry the whole request
    res, err = src.ExecuteMQL(ctx, pipeline)
}

Prevention

Retry idempotent pipeline reads on body-read failures
Check proxy/load-balancer timeouts for large responses
Increase client/context timeout so the body can fully stream

When it happens

Trigger: io.ReadAll(resp.Body) returns non-nil err after httpClient.Do succeeded: the connection dropped while streaming the response, a decompression/reading error occurred, or the deadline expired during body read.

Common situations: Very large pipeline result sets truncated by an intermediate proxy; flaky network dropping keep-alive connections mid-body; timeout elapsing between receiving headers and finishing the body.

Related errors

AI-assisted analysis of googleapis/mcp-toolbox@8cc6e09de2 (2026-09-05). Data as JSON: /api/errors/3d02c154aa9cb767. Report an issue: GitHub.