Environment variables

Variable	Required	Default	Description
FRESHRSS_URL	yes	—	Root URL of the FreshRSS instance, e.g. https://rss.example.com
FRESHRSS_USER	yes	—	FreshRSS user name
FRESHRSS_API_PASSWORD	yes	—	The API password from Settings → Profile → API management
FRESHRSS_READ_ONLY	no	false	true registers only the eight read tools
FRESHRSS_INSECURE_TLS	no	false	true accepts a self-signed certificate, scoped to this connection

There is no configuration file and no command-line flag; these are the whole surface. The reasoning behind each is in Configuration.

Validation at startup

Condition	Result
A required variable is missing	Warning; the server starts and lists tools
FRESHRSS_URL does not parse	Exit 1 (the value is logged with credentials redacted)
FRESHRSS_URL scheme is not http/https	Exit 1
FRESHRSS_URL contains user:password@	Exit 1
FRESHRSS_URL is plain http to a non-loopback host	Warning about the unencrypted API password
FRESHRSS_INSECURE_TLS=true	Warning that certificate validation is relaxed

A missing credential is deliberately not fatal: the server must be able to complete the MCP handshake and answer tools/list without one, so registries and sandbox inspectors can introspect it. Every tool call then fails with the setup instructions. A malformed URL is fatal — that one could send the API password to the wrong host.

All diagnostics go to stderr, which is where MCP stdio servers must log — stdout carries the protocol.

Notes

• Only the exact string true enables FRESHRSS_READ_ONLY and FRESHRSS_INSECURE_TLS; anything else, including 1 and yes, leaves them off.
• Trailing slashes on FRESHRSS_URL are stripped.
• The API path /api/greader.php is appended automatically — do not include it.
• FRESHRSS_API_PASSWORD is deleted from process.env once the configuration has been read, on every path including the ones that then exit. It would otherwise stay readable by child processes and in /proc/<pid>/environ.
• Requests use a 30-second timeout (120 seconds for subscribe_feed and import_opml, which make FreshRSS fetch from the internet first) and refuse to follow redirects.

Limits

Not configurable, but they bound every response:

Limit	Value
Articles per listing	100 (default 20)
Ids per get_articles	20
Articles per mark_articles	100
Article text per article	20 000 characters (default 2000)
Excerpt length	300 characters
Article text per response	60 000 characters
Serialised tool result	400 000 characters
OPML export	200 000 characters
OPML import	900 000 characters
Confirmation token lifetime	5 minutes, single use

The OPML import limit sits below the 1 048 576 bytes FreshRSS reads from php://input — beyond that it truncates silently, which would arrive as malformed XML.