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

Annotations already declare readOnlyHint, idempotentHint, and destructiveHint=false, so safety is covered. The description adds genuinely non-obvious behavior: it explicitly reassures that the call consumes no credits, and it discloses the response contents (active grants and their expiry dates) in the absence of an output schema.

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, both front-loaded with the essential information (what is shown, then the no-credit-consumption caveat). No filler, no repetition of the tool name.

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 zero-parameter read tool with no output schema, the description covers the key facts an agent needs: what is returned and that it is free of side effects. It stops short of describing units or the expiry-date format, which is a minor gap given the simplicity of the operation.

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 and the schema is an empty object, so there is nothing to disambiguate. Baseline for a parameterless tool applies, and the description correctly implies the account scope is implicit rather than something the caller must pass.

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 (show remaining LeadBoxer credits for this account) and even enumerates what is reported: credit count, active grants, and their expiry dates. The sibling tools (lookup_domain, lookup_ip) are in an unrelated domain, so there is no realistic risk of an agent confusing this tool with them.

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 only implied by the nature of the operation; there is no explicit statement of when to call this versus another tool, nor any prerequisite or alternative named. The closing line 'Does not use credits' is a useful caveat but is about side effects, not about when to select the tool.

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