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

With no annotations, the description carries the burden and does disclose the critical trait: no order is created and nothing is charged. That is the highest-value behavioral fact for a pricing tool. It stops short of disclosing auth/permission needs, address-validation failure modes, or rate limits, so it is strong but not complete.

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 sentences, no waste, and the most decision-relevant fact (no order, no charge) is front-loaded. The workflow instruction follows in a single tight sentence.

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 15-parameter tool with no annotations and no output schema, the description covers the safety profile and workflow but says nothing about the parameters or the shape of the returned price. It is adequate for choosing and sequencing the tool but thin on invocation detail.

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 only 47% across 15 parameters, and the description adds no parameter meaning at all. It says nothing about serviceClass, the required recipient fields, content vs contentUploadPath, or the pages/colour/doubleSided pricing inputs, so it fails to compensate for the coverage gap.

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 ('Calculates the exact price of a letter') and immediately scopes it as a non-mutating preview, which cleanly separates it from create_letter_order. An agent can pick it out of the sibling list without reading either schema.

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?

Gives an explicit imperative workflow: always call this (or create_letter_order without confirming) before create_letter_order, and show the price to the user before sending money. It names the alternative path and the ordering condition, leaving nothing to inference.

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