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

readOnlyHint=true already establishes the safety profile, so the description only needs to add context. It adds the useful domain fact that credits are consumed by calls and texts, but says nothing about response shape, error/empty states, or rate-limit behavior for a metered account endpoint.

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?

A single sentence, front-loaded with the verb and resource, with the two returned values enumerated in a compact parenthetical. No filler and nothing to trim.

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 0-param read-only getter with no output schema, the description does the essential work by naming the fields the response contains. It stops short of describing the full response envelope, but an agent has enough to call it and expect account credits and creation date.

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, so there is no parameter semantics to explain; baseline 4 applies. The description's mention of credit and creation-date fields is a useful hint at the payload without competing with any schema documentation.

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?

Specific verb+resource ('Get the account') plus a concrete statement of the two returned facts: credit balance and creation date. It is clearly distinct from the contact/group/call/text siblings, which all operate on other resources, though it does not explicitly say so.

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: the parenthetical that 'calls and texts spend credits' hints this should be checked before sending, but there is no explicit when-to-use statement or exclusion. For a zero-param read-only getter this is tolerable but thin.

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