MCP tool description length: Claude Code 16,384 vs Sume

Claude Code 2.1.295 (Oct 8) now cuts MCP tool descriptions loaded through tool search at 16,384 characters. The old cut was 2,048. If you wrote a long description for your own MCP server, more of it now reaches the model; for Sume's hosted server at https://mcp.sume.com/mcp, the source defines a 2,048-byte limit, so the new cut should rarely matter.

What changed in Claude Code?

The change applies to descriptions that come in through tool search, not to every MCP tool. The changelog gives the two numbers and nothing else about wording or ranking, so do not assume the model reads a long description better than a short one.

How long are Sume's tool descriptions?

Sume's MCP server package defines a 2,048-byte limit for tool descriptions and tests it. That is a source constant, not a promise about the live text. Read the live text with tools_schema for one tool name, or tools_list for all of them.

tools/list returns every tool in one response, so a client does not page through it. The server reports no listChanged push, so a client picks up new tools when it reconnects.

Does a higher cut change what you should do?

For Sume, rarely. The parts of a description that matter are the gates, and they are short: paid and write tools need idempotency_key, dry_run previews cost, and max_spend_usd is enforced only when you send it. Those stay the same at any cut.

If a client still truncates, the fix is the same as before: ask for the contract on demand.

• Call tools_schema with the tool name before the first paid call.
• Keep OAuth on mcp:read for discovery and add mcp:write only for the session that submits.
• Never rely on the description text for a limit. Send max_spend_usd yourself.

What should you check after upgrading?

Run your normal discovery turn once on 2.1.295 and compare the tool list and one schema against the previous version. If the model now quotes a longer description, nothing on the Sume side needs to change. Details of the gates are in MCP tools and gates.