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

No annotations exist, so the description carries the full burden. It does disclose scope boundaries (no ratios, bonus sizes, expiry dates) which is real behavioral context, but it never states that the call is a safe read, says nothing about the `limit`/pagination behavior or result cardinality, and gives no hint about the shape of a returned route.

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 scope limits are stated twice in the space of two sentences — 'does not carry transfer ratios, bonus sizes' and then 'no earning rates, welcome-offer amounts, transfer ratios, or bonus sizes'. In a description this short, a duplicated negation clause is meaningful waste and the 'Card facts only' line muddies the lead.

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 five parameters, no annotations, and no output schema, the description should at least sketch what a returned route contains (source, destination, bonus flag) since nothing else defines the payload. It states the boundaries of the data but not its contents, leaving the agent able to pick the tool but not to anticipate results.

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 all five parameters including the from_program enum and the loosely-matched to_program are already documented in the schema. The description adds only framing about what routes represent, not parameter-level meaning, so the baseline 3 applies.

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 first sentence states a specific relationship (currency → loyalty program transfers) plus the bonus-status check, which is concrete and distinguishable from sibling card-fact tools. However, the closing sentence 'Card facts only — no earning rates...' conflicts with the framing 'This is the route graph only', leaving the agent slightly unsure whether this is a route tool or a card-facts tool.

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 exclusions ('no transfer ratios, bonus sizes, expiry dates, or which route is worth taking') implicitly route the agent to estimate_point_value or compare_card_facts for valuation questions, which is useful. But no alternative is named and no when-to-use trigger is stated, so the routing is left to inference.

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