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

Annotations already declare readOnlyHint=true and openWorldHint=false, so safety is covered; the description nevertheless adds real context beyond them: the result payload (id, network, annual fee, wallet membership, required setup like category picks, memberships, activations) and the hard constraint that the catalog is US-only. It does not discuss result volume or pagination, which matters for an unfiltered "list every card" call.

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, front-loaded with the verb and catalog scope, then examples, then the return shape, then the empty-query rule. No hedging or filler; every clause carries either routing or payload 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?

Complete for a one-parameter read tool: an output schema exists so return values need not be spelled out (the brief summary is a bonus), annotations carry the safety profile, and the description still contributes catalog scope, example queries, and the list-all behavior. Nothing an agent needs in order to call it correctly is missing.

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 format of the single query parameter is already documented, and the description's examples plus "as the user said it" overlap with that. The one genuine addition is that omitting the query returns the full catalog, which the schema cannot express; otherwise 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?

States a specific verb and resource ("Finds credit cards in earnrate's catalog") and scopes the matching keys (name or issuer) with three concrete example queries. It also implicitly separates itself from list_wallet by noting results carry "whether it's already in the wallet," and marks the boundary of the catalog with "US cards only."

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 covers the no-argument case: "Leave the query out to list every card," which is the main branching decision for a single optional parameter. It also routes forward by tagging the returned id as "for add_card." It stops short of naming when to prefer a sibling like list_wallet or best_cards_for over this, so no explicit exclusion is stated.

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