This page is just a reference of all the known Steam APIs, I do not know how they work. Please do not email me with questions.
GETGetSteamCacheNodeParams

Get the operational parameters for a SteamCache node (information the node uses to operate).

https://api.steampowered.com/IContentServerConfigService/GetSteamCacheNodeParams/v1/
NameValueTypeRequiredDescription
click to setstring Yes Access key
uint32 Yes Unique ID number
string Yes Valid current cache API key
POSTSetSteamCacheClientFilters

Update the client filters for a SteamCache node

https://api.steampowered.com/IContentServerConfigService/SetSteamCacheClientFilters/v1/
NameValueTypeRequiredDescription
click to setstring Yes Access key
uint32 Yes Unique ID number
string Yes Valid current cache API key
string Yes Notes
string Yes comma-separated list of allowed IP address blocks in CIDR format - blank to clear unfilter
POSTSetSteamCachePerformanceStats

Update the performance/load stats for a SteamCache node

https://api.steampowered.com/IContentServerConfigService/SetSteamCachePerformanceStats/v1/
NameValueTypeRequiredDescription
click to setstring Yes Access key
uint32 Yes Unique ID number
string Yes Valid current cache API key
uint32 Yes Outgoing network traffic in Mbps
uint32 Yes Incoming network traffic in Mbps
uint32 Yes Percent CPU load
uint32 Yes Percent cache hits
uint32 Yes Number of unique connected IP addresses
uint32 Yes (deprecated) What is the percent utilization of the busiest datacenter egress link?
uint32 Yes What is the percent utilization of the busiest peering link?
uint32 Yes What is the percent utilization of the busiest transit link?