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

With no annotations, the description fully discloses behavioral traits: it requires both confirmation number and a matching email, returns only customer-facing details, and does not expose internal notes or staff fields. It also implies read-only behavior by directing change/cancel requests elsewhere. No contradictions exist.

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 primary action, and every subsequent sentence adds value: required fields, returned data, use cases, exclusions, and alternative tools. It is concise yet comprehensive without being verbose.

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?

Despite having no output schema, the description lists the specific return fields (status, vehicle, pickup/return dates, locations, totals), which informs the agent about expected output. It also covers authentication requirements, use cases, and when to use other tools. For a self-service lookup of modest complexity, the description is complete.

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 coverage is 100%, so the baseline is 3. The description adds emphasis ('Requires BOTH...') and clarifies that the email must match the reservation (renter or cardholder), but this information is largely already present in the schema descriptions. No additional syntax or format details are provided 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 clearly states the tool's purpose: 'Self-service lookup of a customer's own reservation.' It specifies the resource (reservation), the actor (customer), and the typical use cases. It also distinguishes itself from the admin-level lookup_reservation tool.

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?

Explicitly states when to use it: 'Use this to answer what are my dates / where do I pick up / what did I book.' Also gives exclusions and alternatives: 'For changing or cancelling, point the customer to the VIP program' and 'use lookup_reservation (admin) for full staff detail.' This leaves no ambiguity about appropriate usage.

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