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

Annotations indicate this is a mutation (readOnlyHint=false) and not destructive (destructiveHint=false). The description adds context by stating it subscribes the user (a write operation) and requires OAuth. It also explains the behavioral semantics of each alert type (e.g., powder is OBSERVED fresh snow, forecast is a 14-day forecast). This goes beyond the schema and covers the key side-effect profile.

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 long but every sentence carries essential information. It front-loads the core action, then systematically explains each type with its specific criteria. The density is justified by the complexity of five alert types and their scope rules. No fluff or redundancy; it could benefit from bullet formatting, but as prose it is efficient.

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?

This is a complete description for a tool with five parameters and complex type logic. It covers all type semantics, scope formats (including pass syntax), channel defaults, threshold meanings for both powder and forecast, and the windowDays range. It also states the OAuth requirement. Since an output schema exists, no need to describe return values. Nothing an agent needs to call it correctly 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?

The input schema already covers 100% of parameters with descriptions, but the tool description adds meaningful enrichment: it explains the meaning of each enum value for 'type' (e.g., powder = fresh snow >= thresholdCm, trip = powder trip with curated stay) and details the scope options for trips, including pass syntax. This adds value beyond the schema's generic 'Alert type' description.

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 opening sentence, 'Subscribe the signed-in user to snow alerts', states a specific verb and object. It then enumerates the five alert types with precise definitions, which clearly distinguishes this tool from siblings like unsubscribe_alerts and list_alerts. The scope semantics for trips are also spelled out, leaving no ambiguity about what the tool does.

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 explicitly requires a SnowSure OAuth token, which is a critical prerequisite. It defines when each alert type is appropriate (e.g., powder vs forecast vs trip) and gives constraints such as scope 'any' not being accepted for trips. While it doesn't explicitly say 'use this instead of X', the detailed type/scope rules effectively guide selection among related tools.

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