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

With no annotations, the description carries the full burden. It discloses read-only status ('strictly read-only'), token requirement ('Requires a TrueLayer access token'), and mock behavior ('returns structured mock data if no token is configured'). It also details return structure. Missing are error handling and rate limits, but overall it is transparent.

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 description is front-loaded with the action and scope, then return details, usage guidance, exclusions, and auth. It is a single long paragraph but readable. Some redundancy (e.g., 'strictly read-only' after saying no payment initiation) but every sentence adds value. Not maximally concise, but well-structured.

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?

Given no output schema, the description covers return shape (balance, ISO 4217 currency code, up to 100 transactions with date, merchant, amount, category), usage contexts, exclusions, and auth/mock behavior. This is sufficient for an agent to decide invocation and interpret results. Complete for this tool's complexity.

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 the baseline is 3. The description adds context that limit controls transaction count ('up to 100 recent transactions') and mentions optional date filtering, but largely relies on the schema's already-detailed parameter descriptions. No significant additional semantics beyond the schema.

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 ('Retrieves') and resource ('bank account balances and transaction history via PSD2 Open Banking'), naming TrueLayer and its coverage. It explicitly distinguishes the tool from stripe_payments by directing Stripe-related tasks to that sibling, making the 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?

It provides explicit when-to-use scenarios ('inspect a user's spending history, verify a payment has cleared, assess account affordability') and explicit exclusions ('Do not use for payment initiation', 'Do not use for Stripe-specific payment records... use stripe_payments instead'). This is textbook usage guidance.

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