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

Annotations already declare readOnlyHint and non-destructive, and the description reinforces rather than contradicts that with 'Read-only.' It adds value beyond the annotations by disclosing the return payload (balance, cheapest buy-in, top-up page) and the conditional 'when short' branch, which annotations cannot express. No pagination, caching or error behavior is mentioned, but the tool takes no arguments and has no side effects, so little remains to disclose.

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?

Three short sentences, all front-loaded: what it shows, when to call it, and what comes back. Every clause carries information the agent cannot get from structured fields.

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?

No output schema exists, so the description must describe the return value, and it does precisely: the balance, the cheapest buy-in, and a top-up page when funds are short. For a zero-arg read-only tool this is all an agent needs to decide and invoke correctly.

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 of 4 applies. The description correctly adds no parameter detail because there is nothing to parameterize.

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 pair ('Show the user's chip balance and the buy-in of the cheapest table') that no sibling tool covers. An agent can distinguish this from list_tables or join_table without inspecting either 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?

Gives two concrete invocation triggers: a refused seat for lack of chips, or the user asking what they have. The first trigger effectively routes the agent here after a join_table failure, which is the classic confusion case for this sibling set.

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