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

Annotations already declare readOnlyHint=true, so the safety profile is clear. The description adds real behavioral detail: 'newest first' ordering and the supported filters (email, creation time). It doesn't mention pagination or rate limits, but those are covered by the schema's offset/limit parameter descriptions and are less critical for a read-only list operation.

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 short sentences contain all essential information: resource, ordering, filters, and the underlying API endpoint. There is no filler or redundancy. Every clause 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?

For a simple read-only list tool with no output schema and fully documented parameters, the description plus annotations and schema provide everything needed: resource, ordering, filters, pagination token semantics, and read-only safety. Nothing critical is missing.

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 description coverage is 100%; all four parameters have descriptive text including Chargebee mapping notation (e.g., '→ email[is]'). The description only adds a high-level summary of available filters, so it does not meaningfully improve on the schema. Baseline 3 is appropriate.

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 states a specific verb ('List'), resource ('customers'), and key behaviors ('newest first', filters). The sibling list tools like chargebee_list_subscriptions and get_customer are clearly different based on resource and verb, so an agent can tell them apart without opening schemas.

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 gives clear context: use this to list customers with optional email or creation-time filters. It doesn't explicitly say 'use get_customer for a single customer', but the verb 'List' and the sibling names make the intended use unambiguous. No exclusion criteria are stated, so score 4 rather than 5.

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