Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?

Annotations already declare idempotentHint, destructiveHint, openWorldHint and readOnlyHint, but the description adds real context beyond them: the operation is idempotent and replayable, it only admits inbox.receive envelopes, it starts a renewable inbox, and the result can be extended via inbox.extend without changing address or contents. It does not, however, explain the destructiveHint=true aspect (what state may be overwritten or lost), which would be the highest-value addition.

Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

Is the description appropriately sized, front-loaded, and free of redundancy?

Three sentences, front-loaded with the core action and followed by scope and lifecycle notes; there is little waste. Density of domain jargon slightly hurts readability but nothing is redundant.

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

An output schema exists so return values need not be described, and annotations cover the safety profile. However, with nine undocumented parameters and no explanation of the destructive behavior, the definition is only partially complete for a mutating, open-world invocation.

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

Schema description coverage is 0% across 9 parameters (7 required, nested objects), so the description carries the full burden — yet it explains none of them. It only obliquely gestures at the offer restriction ('inbox.receive offer') without clarifying offer_id, offer_revision, digests, idempotency_key, or the parent_binding/attribution objects.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Does the description clearly state what the tool does and how it differs from similar tools?

The description gives a specific verb pair and resource ('Admit or replay one idempotent paid Agent Inbox invocation') plus a scoping constraint ('Only envelopes for the inbox.receive offer are admitted'). It distinguishes this resource from related siblings like inbox.extend, though the heavy jargon ('envelopes', 'settlement authority', 'host boundary') makes the purpose less immediately legible than it could be.

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Does the description explain when to use this tool, when not to, or what alternatives exist?

It states a precondition ('when settlement authority is supplied by the host boundary') and points at inbox.extend as the operation for adding increments while the inbox is active. That implies when this tool is appropriate and how it relates to a sibling, but there is no explicit when-not-to-use or routing between open_inbox and the other inbox tools, leaving usage largely inferred.

Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.