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

Annotations already cover the safety profile (readOnly, idempotent, non-destructive, openWorld), but the description adds substantial context beyond them: the exact auth header format (Bearer ad_agent_<token>), the fact that no arguments/credentials are supplied, the response contents, and the crucial caveat that this is a non-reserving advisory snapshot while server-side admission stays authoritative. Only the lack of any pagination/size or rate-limit note keeps it from a 5.

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?

Five sentences, front-loaded with the core action and scope, then auth, then response, then capability limits, then a caveat. Every sentence carries information, though the closing sentence about receipt recovery is somewhat tangential to selecting/invoking the tool.

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?

With an output schema present, the description needn't enumerate return fields, yet it still summarizes them (scopes, expiry, remaining attempts, credit capacity) and discloses auth requirements, side-effect boundaries, and the authoritative-server caveat. Nothing needed to call this zero-argument read tool correctly is missing.

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?

There are zero parameters, so the baseline is 4; the description reinforces this by instructing the caller to 'supply no arguments or credentials', matching the empty schema with additionalProperties=false. No further parameter meaning is possible here.

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?

States a specific verb (read/inspect), a specific resource (spending grants), and a precise scope ('belonging to the authenticated agent connection'). This is unambiguous and easily distinguished from every sibling, none of which deal with agent grants.

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?

The opening sentence gives clear usage context, and the explicit negative list ('cannot create a grant, fund an account, reserve credits, authorize a purchase or raise a limit') effectively tells the agent when NOT to reach for this tool. It never names a specific alternative tool to use instead, so it falls short of a 5.

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