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

Annotations already cover the safety profile (readOnlyHint=true, openWorldHint=false, destructiveHint=false), and the description adds genuinely non-obvious behavior: a fresh workspace returns zeros rather than an error, and unlimited=true means every credit action succeeds without drawing down available and is never refused for lack of credits. It also discloses the cost model (list price $0.033 per credit and what credits pay for), giving the agent enough context to interpret the numbers without a follow-up call.

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?

It is front-loaded with the resource and its fields, then moves to pricing and the special unlimited case, so an agent can stop reading early if it only needs the basics. The final sentence is long and chains several clauses (free credits, no draw-down, no refusals, no need to check or buy), which slightly hurts scanability but every clause carries real information.

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?

There is no output schema, so the description must carry the return shape, and it does by naming every field an agent will encounter. Combined with the empty-state and unlimited semantics, an agent can interpret any response correctly without extra calls, which is complete for a simple zero-parameter read.

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 meaning to add and the baseline of 4 applies. The description instead spends its space on return-value semantics and edge cases, which is the right allocation for a parameterless getter.

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?

The description opens with a specific verb and resource ("Returns the workspace's credit wallet") and enumerates the exact fields returned: available, reserved, lifetime granted and used, and monthly grant. It is unambiguous about what the tool does, but it never names a sibling such as list_credit_transactions, so an agent gets no explicit differentiation from related credit tools.

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?

It states a clear when-not condition: if unlimited is true, "there is no need to check the balance or buy credits," which directly steers the agent away from calling it and from a purchase path. It also clarifies the expectable state for a new workspace, preventing an agent from misreading zeros as a failure. It stops short of explicit when-to-use phrasing or naming an alternative for transaction history.

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