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

Annotations already declare readOnlyHint, idempotentHint, and destructiveHint=false, so safety is covered; the description adds that the call returns complete prebook data, rate details, terms, and an optional credit balance. It omits auth/permission requirements and rate-limit behavior, but with annotations carrying the safety profile this is a solid contribution.

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 headers are front-loaded and scannable, but the 'What You Get' list is padded with low-information items ('Complete prebook data - All information from the prebook session') and overlaps the Overview. Roughly half the content is genuinely load-bearing.

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?

With no output schema, describing the returned prebook/rate/terms data is genuinely necessary and is provided. Combined with 100% schema coverage and rich read-only annotations, an agent has enough to invoke this correctly; only auth/permission context is absent.

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 both parameters are already documented. The description adds only the mechanical detail that prebookId is a URL path parameter and includeCreditBalance an optional query parameter — useful framing, but no added semantics about identifier format or what value to pass. Baseline 3 is appropriate.

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 Overview states a specific verb and resource: 'Retrieve details of an existing prebook session by its ID,' and contrasts it with session creation ('without creating a new session'), which separates it from the prebook-creating siblings like post_rates_prebook. It stops short of naming a specific sibling it competes with, so it falls just short of a 5.

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 'When to Use' section gives four concrete scenarios (session recovery, status checks, payment integration, credit balance) that tell the agent the right contexts to reach for this tool. It gives no explicit when-not or named alternative, so it is clear context without exclusions.

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