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

Annotations already declare readOnlyHint=true, and the description adds useful non-obvious behavioral facts: the tool is free, requires no account, and returns current pricing so users can evaluate costs before a paid call. This goes beyond the structured annotation without contradicting it.

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?

Two sentences, front-loaded with the most actionable information ('The tool to call first'), and every clause contributes value. No filler or repetition.

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 list tool with no output schema, the description fully covers what the tool returns, why it should be called first, and its cost/free status. An agent has everything needed to invoke it correctly.

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?

There are zero parameters, so the schema leaves nothing to document. The description explains what the tool returns instead, which is appropriate and sufficient for a parameterless metadata endpoint.

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 the specific verb 'Lists' and clearly identifies the resource: phases, timeframes, currencies, and per-phase cards. It also distinguishes this tool from siblings like get_phase by emphasizing that it returns overview metadata and pricing, not a single phase.

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 says 'The tool to call first' and notes it is free with no account, giving clear guidance on when to use it. It does not explicitly name alternatives or exclusions, but the 'call first' directive and pricing purpose provide strong contextual usage guidance.

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