Kuberwastaken/claurst · error

rmcp list_prompts failed

Error message

rmcp list_prompts failed: {}

What it means

Raised in `RmcpClientBackend::list_prompts` when the rmcp peer's `list_all_prompts()` future fails during the `prompts/list` round-trip. Any transport failure or JSON-RPC error response from the MCP server is re-wrapped under a uniform message identifying the backend operation. This mirrors the list_tools/list_resources wrappers and keeps the original rmcp error in the message.

Solutions

1. Check the inner error: 'method not found' means no prompts capability — treat as an empty prompt list.
2. Reconnect the MCP session and retry if the transport closed.
3. Verify the server advertises the prompts capability during initialization.
4. Inspect server logs if the enumeration itself failed.

Example fix

// before: failing hard on prompt listing
let prompts = backend.list_prompts().await?;
// after: degrade gracefully for tool-only servers
let prompts = match backend.list_prompts().await {
    Ok(p) => p,
    Err(e) if e.to_string().contains("method not found") => Vec::new(),
    Err(e) => return Err(e),
};

fn server_supports_prompts(init_caps: &ServerCapabilities) -> bool {
    init_caps.prompts.is_some()
}

match backend.list_prompts().await {
    Ok(prompts) => prompts,
    Err(e) if e.to_string().contains("method not found") => Vec::new(),
    Err(e) => return Err(e.into()),
}

When it happens

Trigger: Calling `list_prompts` when the server rejects `prompts/list`: server lacks the prompts capability ('method not found'), session closed or stale, transport error, or the server errored while enumerating its prompt definitions.

Common situations: Most tool-only MCP servers do not implement prompts, so this fires on nearly every tool-only server; server restarted between connect and the listing; prompt definitions loaded from files that failed to parse server-side; user runs a slash-command discovery pass against a server without prompt support.

Understand the failure class

Background: "API request failed": what wrapped HTTP errors from external APIs mean and how to find the real cause — this error's family across 29 libraries.

Related errors

• rmcp list_tools failed
• rmcp list_resources failed
• rmcp get_prompt ' ' failed
• rmcp call_tool ' ' failed
• rmcp read_resource ' ' failed

AI-assisted analysis of Kuberwastaken/claurst@b0637c97ec (2026-09-10). Data as JSON: /api/errors/6859fc0546222c9e. Report an issue: GitHub.

Appendix: source

Thrown at src-rust/crates/mcp/src/rmcp_backend.rs:557

        let result = self
            .peer
            .read_resource(rmcp_model::ReadResourceRequestParams::new(uri.to_string()))
            .await
            .map_err(|e| anyhow::anyhow!("rmcp read_resource '{}' failed: {}", uri, e))?;
        let first = result
            .contents
            .into_iter()
            .next()
            .ok_or_else(|| anyhow::anyhow!("rmcp read_resource '{}' returned no contents", uri))?;
        Ok(convert_resource_contents(first))
    }

    async fn list_prompts(&self) -> anyhow::Result<Vec<McpPrompt>> {
        let prompts = self
            .peer
            .list_all_prompts()
            .await
            .map_err(|e| anyhow::anyhow!("rmcp list_prompts failed: {}", e))?;
        Ok(prompts.into_iter().map(convert_prompt).collect())
    }

    async fn get_prompt(
        &self,
        name: &str,
        arguments: Option<HashMap<String, String>>,
    ) -> anyhow::Result<GetPromptResult> {
        let mut params = rmcp_model::GetPromptRequestParams::new(name.to_string());
        if let Some(arguments) = arguments {
            let args = arguments
                .into_iter()
                .map(|(key, value)| (key, Value::String(value)))
                .collect();
            params = params.with_arguments(args);
        }
        let result = self
            .peer

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