AI Agent Manifest: Fields, Schema, and Validation Requirements

Why Manifests Matter Before Runtime

As enterprises deploy more autonomous AI agents, a recurring problem emerges: there is often no consistent, machine-readable statement of what an agent is authorized to do before it starts operating. Without that statement, enforcement decisions get made ad hoc, often at the point a tool call is attempted, rather than against a declared baseline. This makes it difficult to answer basic governance questions such as what permissions an agent was granted, whether its behavior matches its intended scope, and who approved that scope in the first place. An agent manifest addresses this gap by requiring identity, capability, and permission information to be declared upfront, in a structured and reviewable form, rather than inferred from runtime logs after the fact.

Core Categories Commonly Found in Agent Manifests

While there is no single universally adopted standard for AI agent manifests at this time, manifests in this space generally organize information into a small number of recurring categories. Identity metadata typically identifies the agent itself, distinguishing it from other agents and establishing a basis for attribution. Capability declarations describe what the agent is technically built to do, separate from what it is currently authorized to do. Permission declarations narrow that capability set down to the specific actions, resources, or data the agent is allowed to access in a given deployment. Tool access declarations specify which external tools, APIs, or systems the agent can invoke, often with conditions attached. Treating these as distinct categories, rather than a single flat list, makes it easier to reason about least privilege: an agent can be technically capable of an action while still being denied permission to perform it.

Schema Structure: What to Expect and What Remains Unsettled

Enterprises evaluating agent manifest formats, including those associated with emerging protocols like the Model Context Protocol, should be cautious about assuming a fully finalized, universally implemented schema exists. In practice, manifest formats in this space are still evolving, and organizations may encounter vendor-specific or protocol-specific variations rather than one settled structure. This is not unusual for a young artifact type. Software supply chain formats such as package manifests and software bill of materials documents went through similar periods of format divergence before conventions stabilized. What matters operationally is not memorizing a specific field list, but ensuring that whatever schema is adopted clearly separates identity from capability from permission, supports versioning as agents and their scopes change, and can be validated programmatically rather than reviewed only by inspection.

Validation: Structural Correctness and Semantic Authorization

Manifest validation generally needs to operate at two levels, a pattern consistent with how declarative permission artifacts are handled in adjacent domains such as API gateways and identity and access management systems.

• Structural validation: confirms that a manifest is well-formed, contains required fields, and conforms to the expected schema.
• Semantic (policy) validation: confirms that the permissions and tool access declared are actually appropriate for that agent, that identity claims are trustworthy, and that nothing in the manifest conflicts with organizational policy.

Structural validation alone is not sufficient for governance purposes. A manifest can be perfectly well-formed and still declare permissions that violate least-privilege principles or grant tool access that was never reviewed. Both validation steps ideally occur before deployment, and permission enforcement should continue to be checked against the manifest at runtime to catch drift between declared and actual behavior.

Risks of Missing, Malformed, or Unvalidated Manifests

When agents operate without a manifest, or with one that has not been validated, several practical risks follow. Enforcement systems have no declared baseline to check tool calls against, which pushes authorization decisions toward implicit trust or reactive blocking after an issue occurs. Audits become harder, since there is no authoritative record of what an agent was supposed to be permitted to do, only logs of what it actually did. Malformed manifests can fail silently in some systems, effectively granting broader access than intended if validation logic does not fail closed. And in environments with many agents, inconsistent or absent manifests make it difficult to apply uniform policy, since each agent's authorization posture has to be reconstructed individually rather than read from a common artifact.

Open Questions for Platform Teams

Several architectural questions remain open and should be resolved deliberately rather than left to default behavior.

• Trust boundary placement: who is authorized to issue, sign, or modify a manifest, and how is that authority enforced technically rather than just procedurally.
• Timing: whether validation happens only at build or deployment time, or is also re-checked at runtime to catch manifests that have been altered or that no longer match an agent's actual behavior.
• Reconciliation: how declared permissions in a manifest are compared against observed tool-call activity over time, so that gaps between what was authorized and what actually happened can be detected and audited rather than assumed away.

Practical Guidance for Manifest Governance

• Separate identity, capability, and permission fields explicitly rather than combining them into a single unstructured block
• Validate manifest structure and policy compliance before an agent is allowed to deploy, not only after an incident
• Define who is authorized to issue or modify a manifest, and enforce that authority technically
• Re-validate manifests at runtime, not only at build or deployment time, to catch drift
• Reconcile declared permissions against actual tool-call activity to support auditing
• Treat manifest format choice as a governance decision, not purely a technical implementation detail

Where Runtime Governance Fits

A manifest establishes what an agent is supposed to be authorized to do. That declaration only has governance value if it is actually enforced and checked continuously while the agent operates, not just reviewed at deployment. This is where runtime governance becomes relevant: verifying agent identity, enforcing declared permissions against real tool calls, and maintaining audit logs that reconcile intended authorization with actual behavior. Trussed AI focuses on this runtime layer, providing policy enforcement, tool approval workflows, and audit logging that work against an agent's declared permissions, so that manifests function as enforceable governance artifacts rather than static documentation.