eSIMCompare: travel eSIM prices

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

The annotations already declare this as read-only, idempotent, non-destructive, and closed-world, so the safety profile is covered. The description adds valuable behavioral context by listing what the comparison returns: plans, destinations, pricing metrics, unlimited-plan share, verdict, and review links.

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?

The definition is two efficient sentences with no filler. It front-loads the comparison purpose and then states the provider-passing rule directly.

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 comparison tool with one optional parameter and no output schema, the description provides enough detail about both the comparison dimensions and the returned information. Nothing critical is missing for an agent to select and call 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?

Schema coverage is 100%, so the single providers parameter is already well documented, including examples and omission behavior. The description adds cardinality and default behavior (one to four, or none for all), but mostly restates what the schema provides.

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 frames the tool as a provider-vs-provider comparison and enumerates the dimensions compared, so the resource and operation are understandable. It does not explicitly contrast itself with siblings like search_esim_plans or esim_price_index, which keeps it from a 5.

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 by the comparison framing, and the description gives practical input guidance: pass one to four providers or none at all. However, it does not state when to choose this tool over the sibling search or price-index tools, or when not to use it.

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

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

Annotations already cover the safety profile (readOnly, idempotent, non-destructive, closed-world), so the description's added value is the data provenance, coverage (193 countries) and the inclusion criteria behind each price. It does not state how fresh the index is or how often it updates, which is the one behavior that would matter for a price tool.

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?

The definition of the measured price is front-loaded before any outcome description, and the two conditional branches are stated in parallel with zero filler. Every clause conveys a constraint or a returned field; nothing is repeated from the title or schema.

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?

There is no output schema, so the description carries the full burden of describing returns, and it does so for both call modes (plan, per-GB price, unlimited week, rank; or median, extremes, provider frequency). With a single optional, fully documented parameter, an agent has everything needed to call 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?

Schema coverage is 100% and the parameter is optional, so the baseline is already met; the description goes further by spelling out what the country value unlocks (rank, per-GB price, unlimited-week price) versus omitting it (aggregate summary). That is output-shaping semantics the schema does not carry.

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 precise measurable thing: the price of a week of mobile data, defined as the cheapest eSIM with ≥5 GB valid ≥7 days, per country, from a named index covering 193 countries. That definition alone distinguishes it from sibling tools that search or compare individual plans, since this returns aggregate price statistics.

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 splits the two usage modes: 'With a country' returns plan-level detail plus rank; 'Without one' returns the global median, extremes and provider frequency. What's missing is a direct routing statement naming compare_esim_providers or search_esim_plans as the alternative when the agent wants a specific plan rather than index data.

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

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

Annotations already cover read-only and idempotent behavior, but the description adds genuinely useful context beyond that: results are sorted cheapest-first, the returned fields are enumerated, prices carry a checked date, and the affiliate_link disclosure clarifies that commissions do not affect pricing. This is meaningful transparency, though it omits anything about coverage gaps, rate limits, or empty-result behavior.

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?

The purpose is front-loaded in the first clause, followed by return fields and then an affiliate disclosure, which is ordered sensibly. It is fairly dense in the middle sentence but every element (sort order, fields, checked date) carries information.

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 usefully enumerates what the response contains (data allowance, validity, price per GB, network, speed policy, source page, buy link), which is exactly what an agent needs. Minor gaps remain around result ordering edge cases and whether the limit applies before or after filtering, but the core picture is complete.

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 description coverage is 100%, so every parameter is already documented in the schema, and the description adds little per-parameter meaning beyond the general 'filtered to what a trip needs' framing. Baseline 3 is appropriate when the schema does the heavy lifting.

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 opens with a specific verb and resource ('Find the cheapest travel eSIM data plans for a destination') and names the provider pool, so the agent knows exactly what the tool returns. It does not explicitly distinguish itself from compare_esim_providers or esim_price_index, so sibling differentiation is left implicit.

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?

Phrases like 'filtered to what a trip needs' imply the tool is for trip-specific plan selection, and the filter parameters reinforce that. However, the description never states when to prefer this over compare_esim_providers or esim_price_index, nor any exclusions or prerequisites.

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