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

The annotations already declare read-only, idempotent, non-destructive, and closed-world behavior. The description adds useful deprecation behavior such as the 12-month sunset, three emailed notices, migration mapping, and one-for-one balance carry-over. However, the GDPR/PECR sentence is unrelated to this tool's behavior and does not add invocation clarity.

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?

The deprecation warning and replacement are front-loaded and efficient. But the final sentence about UK GDPR lawful basis and PECR email audiences is lengthy, unrelated to get_credits, and dilutes the otherwise focused definition.

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?

Given the low complexity, existing output schema, and annotations, the description supplies everything needed: deprecation status, replacement tool, migration path, and sunset timeline. Return values are already covered by the output schema, so no further detail is required.

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 has zero parameters and 100% schema description coverage, so the baseline is 4. The description does not need to explain parameter semantics, and it correctly avoids adding unnecessary parameter detail.

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 'Deprecated: returns the credit balance' and immediately names the replacement, get_account. This gives a specific verb, resource, and deprecation status that clearly distinguishes it from siblings.

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 says 'Use get_account instead' and explains the sunset window, notices, and migration documentation. An agent knows both the preferred alternative and the remaining validity period.

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