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

Annotations already declare readOnly, idempotent, non-destructive, and closed-world, so the safety profile is covered. The description still earns credit by disclosing payload semantics that are invisible elsewhere: cards are masked, monetary fields are { amount, currency } with amount as an exact decimal string, and credit limits/available credit are not spendable cash. It does not discuss pagination limits or result ordering, which keeps it below 5.

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 tight sentences, front-loaded with the operations before the data-format and pagination notes. No filler, though the monetary-format clause is dense and could be split for easier scanning.

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 an output schema present, return values need not be explained, and annotations carry the safety profile. The description covers the remaining agent-critical points: mode selection, masked data, monetary representation, and cursor continuation. Only minor gaps remain around the cursor field name and result limits.

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 mode, where, page, and cardId are all already documented in the schema; the description only restates the find-one/list/filter split. Its one genuine addition is the instruction to pass the cursor back unchanged, but it names that field "page.nextCursor" while the input schema exposes "page.cursor", which blunts the added precision. Baseline 3 is appropriate.

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?

"Find one masked card, list cards, or filter by account or connection" gives specific verbs plus the resource and enumerates all three operating modes, so an agent can immediately tell it retrieves card data (and specifically masked card data) rather than account, transaction, or connection records. The resource distinction from the mofi_accounts_get / mofi_transactions_get siblings is clear from the text itself.

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 maps each intent to an operation (find-one, list, filter by account or connection), and the closing sentence tells the agent how to continue a paged result. It does not state exclusions or name an alternative tool, so it stops short of full when/when-not guidance, but the context needed to pick a mode is present.

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