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

Annotations already indicate readOnlyHint=true, and the description reinforces and extends this by stating 'Reading it does not subscribe anyone' and explaining that sign-up happens on trend.az with the reader confirming terms themselves. This adds useful side-effect context beyond the annotation.

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 sentences: the first defines output, the second gives an explicit call trigger, the third clarifies the non-transactional nature. No redundant words; each sentence adds necessary guidance.

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 simple read-only tool with one optional parameter and an output schema, the description covers what the tool returns, when to invoke it, and the crucial safety caveat. It is complete without needing to restate schema details.

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 single 'lang' parameter is fully described in the schema (which edition's link to return, default 'en', price identical across editions), and the description adds no new parameter-specific meaning. With schema coverage at 100%, the baseline score of 3 is appropriate.

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 clearly states the tool's function: returning subscription costs ('monthly and annual price in manat, dollars and euro'), what it unlocks, and the subscribe link. This distinguishes it sharply from sibling tools that focus on article content, authors, or news listings.

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?

Explicitly tells the agent when to call: 'Call this when a reader asks what a subscriber-only article would cost them, or asks about subscribing.' It also provides a key exclusion, clarifying that the tool does not actually sign anyone up and that sign-up happens externally on trend.az.

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