Limits and quotas

Most surprising SZ-MCP behaviour is a limit doing its job. This page collects them, with what each one does when you reach it.

Timeouts

Limit	Value	On reaching it
code_mode run budget	20 seconds wall clock, shared across every call the program makes	The run is cut off with code_mode exceeded 20000ms wallclock budget, returned as a tool error
One call request to SmartZone	15 seconds	The request is aborted; surfaces as a network_error envelope, and the time still counts against the run budget
Service ticket mint (login)	15 seconds	invalid_host — the controller did not respond in time
API version detection, per candidate	15 seconds	Detection stops; a timeout is not treated as “try the next version”

The run budget is per code_mode call, not per conversation. Every new call gets a fresh 20 seconds, which is why the right response to hitting it is to split the work rather than retry the same program.

There is no per-request CPU accounting

The 20-second budget is wall clock. A tight pagination loop that never waits on the network can still exhaust the underlying Worker CPU allowance before the wall-clock timer fires. Bound your loops explicitly — the examples cap at 5 or 10 pages for exactly this reason.

Sizes

Limit	Value	On exceeding it
code_mode program source	20,000 characters	Rejected before execution: code must be under 20,000 characters
Host / FQDN	253 characters	Rejected on save
SmartZone username	200 characters	Rejected on save
SmartZone password	500 characters	Rejected on save
Credential label	100 characters	Rejected on save

Result caps

These bound what the discovery primitives return in one call. Neither is a cap on what exists — both report the full total separately.

Primitive	Default	Maximum	Total available
search_endpoints	20 results	50	count gives the pre-limit total
list_endpoints_by_tag	50 results	200	count gives the total under the tag

list_endpoints_by_tag takes an offset, so a tag larger than 200 operations is paged rather than truncated. search_endpoints has no offset — narrow the query or add a tag instead.

get_endpoint_details inlines $ref pointers to a depth of 3. Deeper references, and any cycle, are left as { $ref: "…" } rather than expanded.

Caches and lifetimes

Item	Lifetime	Notes
Service ticket	25 minutes	Cached in KV per user, deliberately shorter than SmartZone’s idle timeout. Flushed on credentials save, delete and Test connection
Full OpenAPI spec	Per isolate, until eviction	Loaded from object storage on the first get_endpoint_details for that surface; adds a few hundred ms to that one call
Web session cookie	30 days	szmcp_session
MCP access token	30 days	Prefixed szmk_
MCP refresh token	90 days	Rotated on every use; the old one is revoked
OAuth authorization code	10 minutes	Single use
MCP client registration	30 days	Claude re-registers automatically

Retries

call never throws on an HTTP error, and retries exactly one thing:

Status	Behaviour
401	The cached ticket is discarded, a fresh one is minted, and the request is retried once. A second 401 is returned to you
Everything else	Returned as-is. No automatic retry on 429, 5xx or anything other status

There is no backoff, no Retry-After handling, and no retry budget beyond that single 401 attempt. A rate-limited or flapping controller surfaces directly to the model.

Rate limits

Limit	Value	On reaching it
MCP client registrations	20 per IP per hour	429 with {"error": "rate_limited"}

This bounds the Dynamic Client Registration endpoint only. Normal use registers once per connector, so reaching it usually means something is re-registering in a loop.

Account scope

Limit	Value
SmartZone controllers per account	One
MCP scopes	One — sz:call
MCP tools exposed	One — code_mode

Saving new credentials replaces the stored controller; there is no list of connections to switch between.

Limits that are not SZ-MCP’s

Two ceilings sit outside this service and are worth naming, because they look like SZ-MCP limits from the inside:

• Your SmartZone account’s permissions. Anything it cannot do returns a 403 from the controller. SZ-MCP adds no restrictions of its own — see Security model.
• The controller’s own pagination. WSG list endpoints typically take listSize and index and return { list, hasMore, totalCount }. Those caps are SmartZone’s; SZ-MCP passes your query through unchanged.

Next steps

Code mode primitives The arguments and return shapes these limits apply to.

How code mode works The run budget in context, and why programs should return partial results.

Examples Pagination bounded to stay inside the budget.

Troubleshooting Which limit each error message comes from.