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

Annotations already declare readOnly, idempotent, openWorld, and non-destructive, so the safety profile is covered. The description adds useful framing ('Free', 'no payment or stored session'), indicating a no-auth read, but says nothing about freshness, caching, or result volume.

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 compact sentence that front-loads the key qualifier ('Free') and names the resource. Nothing is wasted, though the telegraphic style trades some readability for brevity.

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 parameterless, non-destructive listing tool with no output schema, the description covers the essentials: what it returns, that it costs nothing, and that no session is stored. Missing only explicit differentiation from pricing_snapshot.

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?

Zero parameters, so there is nothing for the description to explain and the baseline is 4. The empty input schema is consistent with the described no-input listing behavior.

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?

States a clear verb+resource: listing FetchDelta products with current prices and source limitations. Distinguishable from most siblings (diff, resolve, preview_page), though it does not explicitly differentiate itself from the near-neighbor pricing_snapshot.

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 phrase 'No payment or stored session' implies the tool is always available without auth setup, but it never states when to choose this over pricing_snapshot or the other pricing-oriented siblings. Usage is implied rather than guided.

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