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

Annotations already mark the tool as read-only, open-world, idempotent, and non-destructive. The description adds useful behavior beyond that: results are paged at 100 per page and can be filtered by a search term. It also clarifies the data source is the company's connected Xero ledger.

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 two compact sentences with no filler. The first sentence front-loads the core scope, source, and filtering/pagination; the second provides actionable usage guidance.

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 list tool, the description covers what is listed, where it comes from, how filtering and pagination work, and when to use it. The annotations handle safety, and the schema handles parameter requirements, so an agent has what it needs to invoke the tool correctly.

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?

Input schema descriptions cover all three parameters at 100%, so the baseline is 3. The description adds only minor extra meaning—such as the 100-per-page pagination limit and the customer/supplier interpretation—but does not substantially improve on an already complete 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 states a specific verb and resource: 'List contacts (customers/suppliers) from the company's connected Xero ledger'. It also mentions optional search filtering and pagination, which distinguishes it from other Xero tools like list_xero_accounts or list_xero_bank_transactions.

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 second sentence gives clear usage context: 'when the user or an activity needs who the company invoices or pays', including customer/supplier lookups, receivables context, and counterparty verification. It does not explicitly name sibling alternatives or when not to use it, but the conditions are clear.

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