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

Beyond the readOnly/idempotent/non-destructive annotations, it discloses two non-obvious behaviors: the payload contains example prompts and authentication instructions, and no account state is read or mutated. That is genuine added context an agent could not infer from the annotations alone; only the output shape remains unspecified.

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, front-loaded with the value proposition and followed by the return/auth caveat. Nothing is padded, though 'See what signing in adds' is slightly indirect phrasing for a tool named get_account_features.

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 one-optional-parameter discovery tool with no output schema, the description covers what is returned and the no-login constraint, so it is close to sufficient. The notable gap is the unexplained 'topic' enum, plus the tension between the name (get_account_features) and the stated fact that no account is read.

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 0%, and the description never mentions the single 'topic' parameter or its enum (lounge, cruise, points, seats, politics). An agent must guess whether topic filters or scopes the returned feature list, and the enum values are undeclared in both places.

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 concrete purpose: enumerating the optional personal features available after signing in (lounge wallets, home airport, rewards programs, cruise passport, travel map, newsletter prefs), and it clarifies that this is a discovery/marketing surface rather than an account read. It does not name a sibling (e.g. connect_account) as the alternative for actually authenticating, so differentiation is implied rather than explicit.

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?

It gives a clear when-not signal: 'Does not read or change any account; public research needs no login,' telling the agent personalization is unnecessary for ordinary lookups. What is missing is positive routing — it never says to call connect_account (its obvious sibling) when the user actually wants these features enabled.

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