rtk-ai/rtk · error · anyhow::Error

{} is not a JSON file (detected {}). Use `rtk read` for non-

Error message

{} is not a JSON file (detected {}). Use `rtk read` for non-JSON files.

What it means

`rtk json` only processes JSON files. Before reading the file, `validate_json_extension` checks the extension and rejects known non-JSON formats (TOML, YAML/YML, XML, CSV, INI, env, txt) with a message telling you to use `rtk read` instead. For Cargo.toml specifically it also suggests `rtk deps`.

Source

Thrown at src/cmds/system/json_cmd.rs:35

            "toml" => Some("TOML"),
            "yaml" | "yml" => Some("YAML"),
            "xml" => Some("XML"),
            "csv" => Some("CSV"),
            "ini" => Some("INI"),
            "env" => Some("env"),
            "txt" => Some("plain text"),
            _ => None,
        };
        if let Some(fmt) = format_name {
            let mut msg = format!(
                "{} is not a JSON file (detected {}). Use `rtk read` for non-JSON files.",
                file.display(),
                fmt
            );
            if ext == "toml" && file.file_name().is_some_and(|n| n == "Cargo.toml") {
                msg.push_str(" Tip: use `rtk deps` for Cargo.toml.");
            }
            bail!("{}", msg);
        }
    }
    Ok(())
}

/// Show JSON (compact with values by default, or keys-only with --keys-only)
pub fn run(file: &Path, max_depth: usize, schema_only: bool, verbose: u8) -> Result<()> {
    validate_json_extension(file)?;
    let timer = tracking::TimedExecution::start();

    if verbose > 0 {
        eprintln!("Analyzing JSON: {}", file.display());
    }

    let content = fs::read_to_string(file)
        .with_context(|| format!("Failed to read file: {}", file.display()))?;

    let shown = render_json(&content, max_depth, schema_only)?;

View on GitHub (pinned to 36788f6bd4)

Solutions

Use `rtk read <file>` for non-JSON files — that is the recommended tool for them.
Use `rtk deps` if the target is Cargo.toml and you want dependency info.
Verify the file actually is JSON (correct path/extension); convert YAML/TOML to JSON first if needed.
If the file is truly JSON but has a misleading extension, rename it or pipe its content via stdin instead.

Example fix

# before
rtk json config.yaml

# after
rtk read config.yaml   # non-JSON file
# or
rtk json config.json   # actual JSON

Defensive patterns

Strategy: validation

Validate before calling

# check the extension before calling rtk json
case "$file" in
  *.json) rtk json "$file" ;;
  *) rtk read "$file" ;;
esac

Try / catch

# shell
if ! rtk json "$file" 2>err.log; then
  grep -q 'is not a JSON file' err.log && rtk read "$file"
fi

Prevention

Use `rtk json` only for .json files; route TOML/YAML/XML/CSV/INI/env/txt to `rtk read`.
Remember Cargo.toml has a dedicated tool: `rtk deps`.
Never assume YAML is JSON — extensions differ even when content looks similar.
Catch the message pattern 'is not a JSON file' in wrappers to auto-fallback to rtk read.

When it happens

Trigger: Running `rtk json file.toml`, `rtk json config.yaml`, `rtk json Cargo.toml`, or any file whose extension maps to a known non-JSON format (toml, yaml, yml, xml, csv, ini, env, txt).

Common situations: Pointing rtk json at config files by habit (Cargo.toml, docker-compose.yml, .env), confusing JSON with YAML because they look similar, or batch scripts iterating over mixed config files.

Related errors

AI-assisted analysis of rtk-ai/rtk@36788f6bd4 (2026-09-03). Data as JSON: /api/errors/62ee073abbeeadea. Report an issue: GitHub.