agentgateway-cel.md

Agentgateway Objects context

CEL name	Rust field	When / where it’s set
request	request	HTTP request (method, uri, host, scheme, path, version, headers, body, startTime, endTime). Set from live request or from RequestSnapshot.
response	response	HTTP response (code, headers, body). Only set when the executor is built with a response (e.g. new_request_and_response, new_response, or logger with response).
jwt	jwt	JWT claims. Present when JWT auth is enabled and a token was verified.
apiKey	api_key	API key claims. Present when API key auth is enabled.
basicAuth	basic_auth	Basic auth claims (e.g. username). Present when Basic auth is enabled.
llm	llm	LLM context (streaming, models, provider, token counts, prompt, completion, params, etc.). Present for AI backends.
llmRequest	llm_request	Raw LLM request JSON. Present during LLM policies; often not kept for later stages (e.g. logging).
mcp	mcp	MCP resource (e.g. tool, prompt, resource with target/name). Present when the request is MCP.
backend	backend	Backend info: name, type (ai/mcp/static/dynamic/service), protocol (http/tcp/a2a/mcp/llm).
source	source	Downstream connection: address, port, TLS/identity fields (identity, subjectAltNames, issuer, subject, subjectCn).
extauthz	extauthz	Dynamic metadata from ext_authz filters.
extproc	extproc	Dynamic metadata from ext_proc filters.

Agentgateway CEL functions

• contains — check containment
• size — size of string/list/map
• max, min — numeric max/min
• startsWith, endsWith — string prefix/suffix
• string, bytes, double, int, uint — type conversions
• matches — string vs regex
• optional.none(), optional.of(), optional.ofNonZeroValue()
• value, hasValue, or, orValue (on optional values)
• duration, timestamp
• getFullYear, getMonth, getDayOfYear, getDayOfMonth, getDate, getDayOfWeek
• getHours, getMinutes, getSeconds, getMilliseconds
• json, jsonField — parse string/bytes as JSON (or single field)
• to_json / toJson — value → JSON string
• with — variable binding
• mapValues, merge — map operations
• variables — expose all variables (use with care)
• random — float in [0, 1)
• default — fallback when expression can’t be resolved
• regexReplace — regex replace in string
• fail — always fail expression
• uuid — UUIDv4
• base64Encode / base64.encode, base64Decode / base64.decode
• charAt, indexOf, lastIndexOf
• join, lowerAscii, upperAscii
• trim, replace, split, substring
• stripPrefix, stripSuffix
• cidr("...") → .ip(), .masked(), .prefixLength(), .containsIP(...), .containsCIDR(...)
• ip("...") → .family(), .isUnspecified(), .isLoopback(), .isLinkLocalMulticast(), .isLinkLocalUnicast(), .isGlobalUnicast()
• isIP("...") — true if string is valid IP
• flatten — flatten list or map for logging
• flattenRecursive / flatten_recursive — recursive flatten
• precompiled_matches — used when optimizing string.matches(regex) (not something you call directly in expressions)