The surrounding sentence names 2026-07-28 as the revision that first allows
an array-rooted schema, but the link pointed at /draft, which moves on to
the next revision and stops matching the claim.
Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
The spec never uses the phrase "structured output". It defines two separate
things under Tool Result: "Structured Content" (the `structuredContent` field)
and "Output Schema" (the `outputSchema` field). Collapsing them into
"structured output" conflates the two.
It is also actively confusing here. In LLM tooling "structured output" means
constrained decoding — making the *model* emit conforming JSON. These clients
call a model API, so a reader could reasonably take the phrase to mean the
tool constrains the model's response, which is the opposite of what is going
on: the tool describes the shape of its own result.
Headings and prose now say "structured content". References to real
identifiers are left alone: the Python SDK's own docs page is called
Structured Output and lives at docs/servers/structured-output.md, and its
decorator parameter is `structured_output`.
Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Both tools declare an OutputSchema and return StructuredContent alongside the
text.
get_alerts returns []Alert, 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. The declared schema narrows the inferred ["null","array"] root to
"array": jsonschema-go infers the nullable form because a nil slice is valid
Go, but the handler always builds a slice.
Error paths return an error: a tool declaring an OutputSchema MUST return
conforming structured content, so a path with no data has to fail.
The client compiles every declared OutputSchema at connect time and validates
results against it, using jsonschema-go - already an SDK dependency, so no new
one. Each channel goes to its stated reader: Content is forwarded to the
model, StructuredContent is used as data, reporting how many items came back.
The client no longer treats a missing .env as fatal and checks for
ANTHROPIC_API_KEY after connecting rather than before, matching the Python and
TypeScript clients, so the connection can be exercised without credentials.
Requires go-sdk v1.7.0-pre.3: non-object output schema support (SEP-2106)
landed after v1.6.1 and is in no stable release. Model identifier moves to
claude-sonnet-5; the second call in the tool loop used a hardcoded
ModelClaude3_7SonnetLatest while the first used the package variable, so both
now use the same one.
Note that the SDK sends an array-rooted schema as written on every connection
rather than projecting it down, so an older client rejects the tool list.
Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
