Struct A2aAgentConfig 

pub struct A2aAgentConfig {
    pub name: String,
    pub url: String,
    pub headers: BTreeMap<String, SecretString>,
    pub allow_plaintext_credentials: bool,
    pub limits: A2aLimits,
}

Configuration for one remote agent reached over A2A.

Which URL

url names the agent in one of two ways, told apart by its path alone:

• A base URL — path / (or none) and no query, such as https://nous.example.com. The card is fetched from WELL_KNOWN_AGENT_CARD_PATH on that origin, where the specification says an agent publishes it.
• A card URL — anything else, such as https://example.com/agents/nous/card.json, is fetched as given.

Well-known paths only exist at an origin’s root, so a URL with a path is never a base for one; there is no third case to guess at.

Example

use mentra::a2a::A2aAgentConfig;

let config = A2aAgentConfig::new("nous", "https://nous.example.com")
    .with_bearer_token("<token>");
assert_eq!(
    config.card_url().unwrap().as_str(),
    "https://nous.example.com/.well-known/agent-card.json",
);

Security

Header values are stored as SecretString and never appear in Debug output, error messages, or logs. They are sent on the card fetch and on every call. Configuring a header on a plaintext http:// URL is rejected unless the host is loopback — the same rule, with the same override, as the MCP HTTP transports — and the rule is applied again to the interface URL the card names, because that URL is chosen by the remote side rather than by the operator.

Fields

name: String

The agent’s local name, which names its tool a2a__{name}.

url: String

The agent’s base URL or card URL; see Which URL.

headers: BTreeMap<String, SecretString>

Headers sent on every request to the agent.

allow_plaintext_credentials: bool

Permits sending configured headers over plaintext http:// to a non-loopback host.

This exists so the refusal is overridable but never accidental.

limits: A2aLimits

Timeouts and size limits, defaulted rather than deserialized.

Implementations

impl A2aAgentConfig

pub fn new(name: impl Into<String>, url: impl Into<String>) -> A2aAgentConfig

Creates a configuration with default timeouts and limits.

pub fn with_header( self, name: impl Into<String>, value: impl Into<SecretString>, ) -> A2aAgentConfig

Adds a header sent on every request to the agent.

pub fn with_bearer_token(self, token: impl Into<String>) -> A2aAgentConfig

Adds a bearer Authorization header.

pub fn with_limits(self, limits: A2aLimits) -> A2aAgentConfig

Replaces the timeouts and size limits.

pub fn allowing_plaintext_credentials(self) -> A2aAgentConfig

Permits sending configured headers over plaintext http://.

pub fn card_url(&self) -> Result<Url, A2aConfigError>

The URL the Agent Card is fetched from; see Which URL.

pub fn validate(&self) -> Result<Url, A2aConfigError>

Validates the configuration and returns the card URL.

Checks the name, URL, header names and values, credential handling and limits without connecting, so a host can reject a bad configuration at its own boundary rather than discovering it on the first request.

Trait Implementations

impl Clone for A2aAgentConfig

fn clone(&self) -> A2aAgentConfig

Returns a duplicate of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl Debug for A2aAgentConfig

Hand-written so no {:?} of a config prints a credential. Header values are SecretStrings and redact themselves; url is a plain String, and its userinfo and query string are where a credential would sit, so both are replaced. String surgery rather than a URL parser: Debug must never fail, and an unparseable URL is exactly what someone will debug-print.

fn fmt(&self, f: &mut Formatter<'_>) -> Result<(), Error>

Formats the value using the given formatter.

impl<'de> Deserialize<'de> for A2aAgentConfig

fn deserialize<__D>( __deserializer: __D, ) -> Result<A2aAgentConfig, <__D as Deserializer<'de>>::Error>

where __D: Deserializer<'de>,

Deserialize this value from the given Serde deserializer.

impl From<A2aAgentConfig> for A2aAgent

fn from(config: A2aAgentConfig) -> Self

Converts to this type from the input type.