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

Annotations already establish the safe, idempotent, closed-world read profile, so the description's added value matters: it discloses the exact count (five), the template contents, that rates are illustrative USD cents rather than pricing advice, and that no account is required. That is useful context beyond the annotations, though return format or pagination is not discussed (not applicable here).

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 tight sentences: the first front-loads the core purpose and contents, the second carries the two caveats (cents, not advice) and the no-account note. No filler.

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 zero-parameter, read-only listing tool with no output schema, the description covers what is returned and how to interpret the numbers. It could say more about the response structure, but that gap is minor given the tool's simplicity.

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 tool takes zero parameters, so the baseline is 4. The description goes slightly further by clarifying that embedded rate values are in USD cents and are examples, which helps interpret the returned data even though no inputs exist.

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 (list) and resource (editable sample invoice templates), and enumerates the five template types so an agent knows exactly what it will get back. It doesn't explicitly contrast itself with siblings like prepare_invoice_template, but 'sample' and 'editable' make the read-only example-listing role reasonably distinct.

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?

Usage is implied rather than stated: the fixed set of sample invoices and the note 'No account needed' suggest exploratory/browsing use, but there is no explicit when-to-use or when-to-prefer-a-sibling such as prepare_invoice_template or draft_invoice.

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