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

Annotations already declare a non-read-only, non-destructive, non-idempotent, open-world operation. The description adds real value beyond that: 'Nothing is charged by calling this' reassures the agent no monetary side effect occurs, which is not derivable from the hints. It omits that repeated calls create multiple distinct links (relevant given idempotentHint=false).

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?

Three short sentences, front-loaded with the action and return value, with zero filler. Every sentence 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?

An output schema exists so return values need no explanation, and the description still notes the URL is the key output. For a one-parameter create tool the coverage is strong; missing only edge details such as link expiry or auth requirements.

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 single parameter's description ('A code from list_packages') already routes the agent to the correct source. The prose adds nothing about package_code, so baseline 3 applies.

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?

Specific verb+resource: 'Create a payment page for a traffic pack and return its URL.' The outcome (a URL) is stated up front, which cleanly separates it from siblings like start_download, get_download_link, and check_link.

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?

'Give the URL to the user: only a person can pay it' tells the agent what to do with the result and that the agent itself cannot complete payment. It does not name alternatives or explicit when-not conditions, but the context is clear and actionable.

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