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

Annotations already declare readOnlyHint, idempotentHint, and destructiveHint, so the safety profile is covered. The description adds useful behavioral details: it operates on an 'active pass', explains wallet_type selection for Apple/Google, and clarifies that it shares the same HTTP API, billing, and rate limits as the underlying PassFast API. This supplements the annotations meaningfully.

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 description is compact and front-loaded: the first line states the core purpose, followed by a brief qualifier on wallet selection, then scope, API mapping, and a caution. Each sentence adds value with no redundant 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 download tool with no output schema, the description sufficiently covers the purpose, wallet_type disambiguation, scope, and API context. It omits explicit error handling or authentication details, but the annotations and simple parameter set make those gaps minor. The added billing/rate-limit note improves completeness.

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%, and the schema already documents all parameters, including wallet_type's role and default. The description repeats the wallet_type behavior without adding new meaning; it does not further elaborate on formats or constraints beyond what the schema provides. Baseline 3 is appropriate when the schema carries the parameter semantics.

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 (Download) and a specific resource (`.pkpass` by serial number), and distinguishes from siblings like downloadPass or downloadSharedPass by keying on serial number. It also maps to a specific OpenAPI operation, leaving no ambiguity about intent.

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 gives clear context for the wallet_type parameter and its default, but it does not explicitly instruct when to use this tool instead of alternatives such as downloadPass or downloadSharedPass. The usage is implied by the serial-number-based purpose, but no exclusions or alternative routing are provided.

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