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

No annotations are provided, so the description carries the behavioral burden. It does disclose an important limitation: no ratios, bonus sizes, expiry dates, or route-valuation guidance. It also states that the route graph only shows existence and bonus running status. However, it doesn't say what the actual output looks like (since there is no output schema), nor mention that to_program is loosely matched while from_program has strict enum values, which is relevant behavioral nuance.

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?

Two dense sentences, front-loaded with the main capability and then negative scope limitations. Every clause earns its place; the text is compact but informative. No fluff.

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 read-only search tool with fully documented parameters, the description is nearly complete. The main gap is the absence of output-shape information, but since there is no output schema anywhere, even a brief note on what a route row looks like would help. Also, despite having 5 parameters and 1 enum, the description gives enough guidance for an agent to call it correctly. The lack of an output schema makes this less complete than a tool with a rich output schema, but it is still strong.

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 input schema already explains all 5 parameters with 100% coverage, so the baseline is 3. The description adds value beyond the schema by clarifying that the route graph does not include transfer ratios or bonus sizes, which prevents an agent from misinterpreting a route result as a recommendation. It also reinforces that calling with neither argument lists every source, which is not stated in the schema. This pushes it to a 4.

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 names the exact resource (route graph of loyalty currency/program transfers) and the key actions it supports: finding where a currency transfers, what reaches a destination, and whether a bonus is running. It also explicitly distinguishes itself from card-facts sibling tools by saying 'Card facts only — no earning rates, welcome-offer amounts, transfer ratios, or bonus sizes.' This makes the tool's purpose unmistakable.

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 description provides strong context for when to use the tool: when you need routes, not ratios or bonus sizes. It does not name alternative sibling tools like estimate_point_value or compare_card_facts explicitly, but it clearly says what the tool does NOT cover, which effectively steers an agent away from using it for those questions. Slightly missing an explicit 'use X instead' statement for those cases.

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