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

Annotations already declare readOnlyHint=true, openWorldHint=true and destructiveHint=false. The description adds real value by clarifying that the tool only returns options plus a checkout path rather than performing a subscription or payment itself, which corrects the expectation set by the imperative name; it also implicitly explains why openWorldHint is true. It still omits whether authentication or an existing account is required.

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?

A single well-formed sentence with the resource and outcome front-loaded and no redundancy. Mild promotional phrasing ('advanced analytical tools') is the only 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 zero-parameter tool with no output schema, the description covers the essentials: what comes back (subscription options and a checkout path) and what it enables. Slightly more detail on the shape of the return (e.g. whether the path is a URL) would close the remaining gap.

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 takes zero parameters, so there is no parameter semantics to document and the baseline applies. The description correctly implies the call is argument-free and returns a result set rather than requiring input.

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 pairs a specific verb ('Returns') with a specific resource ('FXMacroData subscription options and a direct checkout path') and names the payoff (MCP visuals, charts, analytical tools). It is clearly not a data-query tool, so an agent can separate it from catalogue_search or mcp_capabilities, though it never explicitly says so.

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?

Usage is implied rather than stated: an agent can infer this is for when a user wants to unlock paid MCP features. There is no explicit when-to-use framing, no mention of the free alternative (e.g. mcp_capabilities for capability discovery), and no note on prerequisites or follow-up steps.

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