Find where mobile proxies are available

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

Annotations already declare readOnlyHint=true and openWorldHint=true, so safety is covered. The description adds genuinely non-obvious behavioral detail: prefix matching on word starts, Cyrillic/Latin input acceptance, and the quirk that captions are mostly English with some Russian while operator names are API ids like 'megafone' and 'beeline'. It does not discuss pagination or what happens when more locations exist than the limit.

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?

Front-loaded with the core question it answers and what it replaces, then supporting detail on input formats and downstream use. It is dense but every sentence carries either routing, matching, or data-shape information. The embedded quoted question is slightly verbose but earns its place by framing the use case.

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?

With no output schema, the description carries the return-value burden and does so: locations with free modems, operators with free modems, prices per rental period, plus the reusable geoid and operator ids. What it omits is result-size behavior relative to the limit parameter and how to interpret an empty result, which an agent would need for a complete picture.

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?

Schema coverage is 83%, so most parameters are already documented. The description still adds value beyond the schema by explaining the matching rule for city and operator (start of a word in the caption / operator name) and that operator values are API ids rather than display names. The currency, limit and min_free parameters get no extra narrative, but their schema descriptions are sufficient.

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 states a precise verb+resource ('answers where can I get a mobile proxy in <country/city> on <operator>, and what does it cost in one call') and explicitly distinguishes itself from sibling tools by naming the chain it replaces: get_geo_list, operator lookups and get_price. An agent can route to it without opening any schema.

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?

It gives a concrete when-to-use condition (you need locations, free modems per operator, and prices together) and names the alternatives it supersedes. It also closes the loop on downstream usage by stating the returned geoid and operator feed the purchase and change_geo tools, so the agent knows this is a lookup step, not a purchase step.

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