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

Annotations already declare readOnlyHint=true, idempotentHint=true, and destructiveHint=false, so the safety profile is covered. The description adds the OAuth requirement, which is an important behavioral constraint not present in the annotations. It does not contradict any annotation, and it clarifies the read-only nature by describing returned information.

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?

Two sentences with zero wasted words. The most important information (what is returned) is front-loaded, and the OAuth requirement is stated succinctly at the end. Every word earns its place.

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?

With no output schema, the description appropriately lists all the return aspects (balance, status, level progress, available write-off) and states the auth prerequisite. The optional parameter is documented in the schema, and the tool is simple enough that no further behavioral details are needed for correct invocation.

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?

Schema coverage is 100% and the schema description for cart_total_rub already explains it as the order amount to calculate available write-off. The tool description mentions the parameter indirectly but adds no new meaning beyond the schema. Baseline 3 is appropriate since the schema carries the semantic load.

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 clearly enumerates the specific data returned (bonus balance, customer status, progress to next level, and available discount for a given order amount), making it unambiguous that this is a read-only loyalty query. It is easily distinguished from siblings like my_orders or build_cart, which deal with orders or cart operations.

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?

The description clearly states what the tool does and that OAuth login is required, which gives an agent strong context for when to invoke it. It does not explicitly name alternatives or say 'use this instead of X', but the purpose is so distinct from the sibling tools that the usage context is clear without exclusions.

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