test: every array-typed MCP argument must deliver its values to the API

[leggetter]

The follow-up #455 names in its Not covered section.

#455 makes every read that treats an MCP argument as a list go through StringList, so a bare or comma-separated string is never dropped. It cannot see the reverse: a handler that declares an argument as an array and reads it with in.String(), which returns "" for an array and drops it without an error.

What this adds

A test on each server that:

• finds every array-typed argument from the live tool schemas, with writes enabled;
• requires each to have a valid call in a table;
• sends a genuine JSON array to a recording server, and requires every value to reach the request.

A new array argument fails until it has an entry; a stale entry fails too. The expected strings are the encodings captured from the recording server, not assumed.

Today

Ten array arguments, and all ten deliver correctly — a guard, not a fix.

Server	Arguments
Gateway	metrics_read.measures, metrics_read.dimensions, request_write.connection_ids, connections_write.rules
Outpost	attempts_read.include, config_write.unset, destinations_read.topics, destinations_write.topics, metrics_read.measures, metrics_read.dimensions

Proven against the failure

• Reading connection_ids with in.String() fails the Gateway test — and the recorded request shows why it matters: the retry goes out as {}, meaning retry every connection, instead of the two chosen. A silent widening of a write.
• Reading include with in.String() fails the Outpost test.
• Removing a table entry fails with a message naming the argument.

CI's unit-test steps (go test -short ./pkg/..., go vet ./...) pass locally by exit code.

Intended for v3.0.3.

🤖 Generated with Claude Code

https://claude.ai/code/session_012XtSQ2kfpcRXXqweskgXkH