Worker tokens
A worker gets a bearer token from one of three sources, chosen per worker when you add it.
Most real workers want a bearer token. You never paste it into Claude. When you add the worker, you tell the mod which of three places to read it from.
Three sources
Pick the source when you run /a2a add. With no flag, the mod uses the tokens setting. Give a worker at most one token flag.
| Flag | Source | Notes |
|---|---|---|
--token-setting | The tokens setting | The default. alias=token pairs separated by spaces. |
--token-cmd "<command>" | A command's output | Run without a shell. Cached for 5 minutes. |
--token-file <path> | A file | Keep it at mode 0600. Cached for 5 minutes. |
The tokens setting
The setting holds alias=token pairs separated by spaces. The mod looks up a worker's token by its alias. Set the setting from a shell, then restart Claude Code:
claude plugin configure a2a-mod@a2a-mod --values-stdin <<< '{"tokens":"w1=<token>"}'This replaces the whole setting, so list every worker in it: "w1=<token> w2=<token>".
If the mod's id is not a2a-mod@a2a-mod, use the id that claude plugin list shows.
If any word in the setting is not alias=token, the mod ignores the whole setting, and /a2a list prints a warning.
Command and file
--token-cmd runs a command without a shell and uses its output as the token. The mod splits the command on spaces; wrap an argument in double quotes to keep it as one word.
/a2a add https://worker.example.com w1 --token-cmd "op read op://vault/w1/token"
/a2a add https://worker.example.com w2 --token-cmd "pass show w2"
/a2a add https://worker.example.com w3 --token-cmd "gh auth token"--token-file reads the token from a file. Keep it at mode 0600:
/a2a add https://worker.example.com w4 --token-file ~/.config/a2a/w4.tokenCommand and file tokens are cached in memory for 5 minutes. The mod fetches them again after a 401 or 403 from the worker.
The command line is stored and shown by /a2a list. Its output is never shown. The mod gives the command 10 seconds to finish.
Workers Claude adds
A worker that Claude adds with the add_worker tool uses the tokens setting and nothing else. If the card asks for a token and the setting has none for that alias, Claude tells you how to set it. For a command or file token, or for --trust-endpoint, run /a2a add yourself. A worker's reply can carry prompt injection, so Claude is never given a way to choose where a token comes from.
Where a token goes
A token goes only to the origin of the worker's Agent Card. If the card points to an endpoint on another origin, the mod withholds the token until you re-add the worker with --trust-endpoint. That flag allows the token to go to an endpoint on another origin than the card, and it is separate from the three sources.
Never type a token
Never type a token into Claude or into `/a2a`
Slash commands are kept in the transcript, so /a2a add rejects --token.
For where each source is kept and what counts as a vulnerability, see Security.