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

With readOnlyHint already declaring this a safe read, the description adds real context: what states the call surfaces (probation, pauses, pending review) and an important domain rule that purchasing credits does not lift sending controls. It does not describe the response shape, but the behavioral caveat is the valuable part.

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?

Two short sentences with no waste. The primary purpose is front-loaded and the credit caveat follows as a secondary, non-redundant point.

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?

For a parameterless read tool with no output schema, the description covers what the agent needs: what is read and which states may come back. A note on the shape of the returned status (e.g., a state value plus limit numbers) would make it complete.

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?

The tool takes zero parameters, which is the baseline-4 case; there is nothing for the description to disambiguate and it correctly presents the tool as a no-argument query.

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 and resource: 'Read your sending state and current limits', and enumerates the sub-states covered (probation, pauses, pending review). It is distinguishable from check_balance and check_payment, though it does not explicitly name those siblings.

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?

Usage is implied: an agent should call this before/alongside sending to learn whether sending is currently permitted. There is no explicit when-to-use or when-not-to-use guidance, and the nearby alternatives (check_balance, check_payment) are never mentioned.

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