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

Annotations already declare readOnlyHint, idempotentHint, and destructiveHint=false, so the safety profile is covered. The description adds genuinely new behavioral context the annotations cannot express: the tool is deprecated and scheduled for removal in 0.9, which should influence an agent's choice. It still says nothing about the returned data shape or whether the value is stale/live.

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 short sentence, front-loaded with 'Deprecated' so the most decision-relevant fact lands first. Every clause (replacement name, its advantage, removal version) carries information; nothing is filler.

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 simple no-parameter read tool with full annotation coverage, the deprecation and migration guidance covers the main decision. However, there is no output schema and the description never says what the balance response contains, so an agent cannot judge whether the replacement returns comparable data.

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 schema takes zero parameters, so there is nothing for the description to disambiguate; the baseline for a parameterless tool applies. No parameter claims are made or contradicted.

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 never states what the tool actually returns; the only clue is the name and title ('Credit balance'). It devotes its whole text to deprecation status and a migration path, so an agent must infer the function from the identifier rather than from a stated verb+resource.

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 explicitly names the replacement (billing_status) and adds why ('which also shows plan and free allowance'), plus a lifecycle horizon ('Removal planned for 0.9'). What's missing is an explicit statement of whether the tool still works today or should be avoided entirely, though the removal timeline implies it is still callable.

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