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

Annotations already indicate the tool is open-world, idempotent, and non-destructive. The description adds valuable context that it opens a page (not directly modifying the plan) and that the plan can be changed from that page. This goes beyond the annotations without contradicting them.

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 a single, well-structured sentence that front-loads the core action and then provides the usage condition. Every word earns its place with no redundancy.

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 tool with no parameters and no output schema, the description is completely sufficient: it explains what the tool does, what page it opens, and when to call it. There are no gaps in understanding.

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 tool has zero parameters, and the schema covers everything (100% coverage). The description still contributes by clarifying the action's intent, though no parameter details are needed. This aligns with the baseline for parameterless tools.

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 uses a specific verb ('Open') and specifies the resource ('GlassyPic pricing page'), clearly distinguishing this from sibling tools like login, logout, status, and optimize_image. It states exactly what the tool does and why it exists.

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 explicit when-to-use guidance: 'Call this only when the user asks to change or review their plan.' This is a clear directive that also implies when not to use it, making it easy for an agent to decide.

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