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

Annotations already declare readOnly, idempotent and non-destructive, so the safety profile is carried structurally. The description still adds value by disclosing the zero-credit cost of the call and the account-level ('shared') scope, which the annotations do not express.

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?

One front-loaded sentence with the verb, resource, returned fields and cost caveat all present. No filler, 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?

Zero-argument read with an output schema, so the description needn't document returns or parameters. It covers what is left: what account state is read, the 'shared' scope, and that the call is free.

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?

Zero parameters, so the baseline is 4. The description correctly claims nothing in the way of arguments, and 'shared' usefully signals there is no user/workspace selector to 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?

Specific verb 'Read' plus specific resource 'shared REST/MCP credit balance' with the exact sub-fields returned (monthly/prepaid split, reservations, pause state). None of the sibling tools touch account state, so an agent can route to it without opening the schema.

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?

'Without spending credits' implies this is the cheap upfront check before calling paid query siblings, but the connection is never stated and no sibling is named. Usage is inferable rather than instructed; there are no explicit exclusions or alternatives.

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