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Stamp the required resultType on modern results per SEP-2322

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## Motivation and Context

SEP-2322 (merged for the 2026-07-28 spec release) makes `resultType` a REQUIRED member of every result
a 2026-07-28 server returns: "Servers implementing this protocol version MUST include this field",
with absence tolerated only when the result comes FROM an earlier protocol version.
The client-side vocabulary landed earlier (`MCP::ResultType`, treating an absent value as `"complete"`),
but every ordinary modern result the server returns is unstamped, which violates the MUST for `tools/list`,
`tools/call`, `ping`, and every other standard result on the modern wire.
The conformance suite's 2026-07-28 requirements fail each of those scenarios on wire-schema validation
(`CallToolResult: must have required property 'resultType'`).

The dispatch path now stamps `resultType: "complete"` centrally: any Hash result of a request carrying
the SEP-2575 `_meta` envelope that does not already carry a `resultType` gets the standard value merged in.
Results that already carry a discriminator keep it, notifications and cancellation-suppressed responses
are untouched, and legacy results stay unstamped because pre-2026 clients do not know the field.
`server/discover`, which is exempt from the `_meta` envelope (pre-version discovery),
stamps its `DiscoverResult` at its construction site instead.

## How Has This Been Tested?

`bundle exec rake test` passes with zero failures. New tests in `test/mcp/server_test.rb`: `tools/list`,
`ping`, and `tools/call` results carry `resultType: "complete"` on modern requests and no `resultType`
on legacy requests; `server/discover` carries the stamp. The conformance scenarios previously failing
on the missing property (`tools-call-simple-text`, `prompts-get-simple`, `completion-complete`, and
the other tools/prompts scenarios) pass at `--spec-version 2026-07-28` against the conformance fixture server.

## Breaking Changes

None. The stamp applies only to results of requests carrying the SEP-2575 modern `_meta` envelope;
results on stable protocol versions through 2025-11-25 are byte-for-byte unchanged.
This commit is contained in:
Koichi ITO 2026-07-05 02:24:20 +09:00
commit 14bf3a7091
1 changed files with 61 additions and 1 deletions
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42
test/mcp/server_test.rb
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@ -4142,6 +4142,42 @@ module MCP
refute Apps.client_supports?(server.client_capabilities)
end
# SEP-2322 makes `resultType` REQUIRED on every result of a 2026-07-28 server;
# `"complete"` is the standard shape, and legacy results stay unstamped.
test "modern results carry resultType complete" do
server = Server.new(name: "result_type_test", tools: [result_type_tool])
[
modern_request(Methods::TOOLS_LIST, {}),
modern_request(Methods::PING, {}),
modern_request(Methods::TOOLS_CALL, { name: "result_type_tool", arguments: {} }),
].each do |request|
response = server.handle(request)
assert_equal "complete", response.dig(:result, :resultType), "expected stamp for #{request[:method]}"
end
end
test "legacy results carry no resultType" do
server = Server.new(name: "result_type_test", tools: [result_type_tool])
[
{ jsonrpc: "2.0", method: Methods::TOOLS_LIST, id: 1 },
{ jsonrpc: "2.0", method: Methods::PING, id: 2 },
{ jsonrpc: "2.0", method: Methods::TOOLS_CALL, id: 3, params: { name: "result_type_tool", arguments: {} } },
].each do |request|
response = server.handle(request)
refute response[:result].key?(:resultType), "expected no stamp for #{request[:method]}"
end
end
test "server/discover carries resultType complete" do
server = Server.new(name: "result_type_test", tools: [result_type_tool])
response = server.handle({ jsonrpc: "2.0", method: Methods::SERVER_DISCOVER, id: 1 })
assert_equal "complete", response.dig(:result, :resultType)
end
private
# Builds a request carrying the SEP-2575 modern `_meta` envelope.
@ -4159,5 +4195,11 @@ module MCP
),
}
end
def result_type_tool
@result_type_tool ||= Tool.define(name: "result_type_tool") do |**|
Tool::Response.new([{ type: "text", text: "ok" }])
end
end
end
end