Add structured output to the TypeScript weather server and client#165
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Both tools declare an outputSchema and return structuredContent alongside the
text.
get-alerts declares z.array(...), so it answers with a top-level JSON array
rather than an array nested in an object, which protocol revision 2026-07-28
is the first to allow. "No alerts" is simply []. get-forecast returns an
object, for contrast.
This costs older clients nothing. The server declares the array schema once
and never branches on protocol version: serveStdio serves both eras from one
factory, and the SDK projects the schema down to
{"type":"object","properties":{"result":...}} for a 2025-11-25 client, wrapping
the structured content to match. Verified against both eras.
Error paths throw: a tool declaring an outputSchema MUST return conforming
structured content, so a path with no data has to fail.
The client passes versionNegotiation {mode:"auto"}; the SDK default is
"legacy". The SDK validates every result against the declared schema, so the
client-side SHOULD needs no code. Each channel goes to its stated reader:
content is forwarded to the model, structuredContent is used as data,
reporting how many items came back.
Moves to the 2.0 beta packages, where the 2026-07-28 support lives:
@modelcontextprotocol/sdk is replaced by @modelcontextprotocol/server and
@modelcontextprotocol/client. Model identifier moves to claude-sonnet-5.
Co-Authored-By: Claude Opus 5 <[email protected]>
This was referenced Jul 26, 2026
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Brings the TypeScript examples onto MCP SDK 2.0 and protocol revision
2026-07-28, and gives both tools a declaredoutputSchemawith matchingstructuredContent.get-alertsanswers with a top-level JSON array:[ { "event": "Flood Warning", "area": "La Salle County", ... }, { "event": "Heat Advisory", "area": "Wheeler County", ... } ]Through
2025-11-25anoutputSchemahad to be object-rooted, so a tool returning a list had to invent a key to hang it off.get-forecastreturns an object, for contrast.This costs older clients nothing
The server declares the array schema once and never branches on protocol version.
serveStdioserves both eras from one factory, and the SDK projects the schema for whichever era connects.A
2026-07-28client sees the schema as written. A2025-11-25client sees{"type":"object","properties":{"result":{...}}}and getsstructuredContentas{"result":[...]}. Verified against both.Other changes
Error paths throw. A tool declaring an
outputSchemaMUST return conforming structured content, so a path with no data has to fail rather than answer with a bare text result.The client negotiates.
versionNegotiation: { mode: 'auto' }probesserver/discoverand falls back to the2025-11-25handshake; the SDK's default is'legacy'.Each channel goes to its stated reader.
contentis forwarded to the model;structuredContentis used as data, reporting how many items came back. The SDK validates it against the declared schema, so the client-side SHOULD needs no code.Package split.
@modelcontextprotocol/sdkbecomes@modelcontextprotocol/serverand@modelcontextprotocol/client, which is where the2026-07-28support lives. Model identifier moves toclaude-sonnet-5.Verification
Captured off the raw wire — a real
get-alerts("TX")call against live NWS data, no SDK on the client side:Related
One of a set bringing the examples onto
2026-07-28, one PR per language so the four can be compared: #164 (Python), #165 (TypeScript), #166 (Go), #167 (Rust). #163 is the shared prerequisite. CI here is green, which is itself worth noting:main's smoke test uses an MCP SDK v1 helper that negotiates2025-11-25, and it accepts this server because the SDK projects the array-rooted schema down to the object form that revision expects. The behaviour described above, confirmed by a real v1 client. Extending that test to assert on structured output comes with #163.The Ruby examples are deliberately not in the set: the
mcpgem caps at protocol2025-11-25.🤖 Generated with Claude Code