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

With no annotations at all, the description carries the full burden, and it does disclose real behavioral facts: 'Enquiry-led: no price is quoted and nothing is charged online' tells the agent this is a non-transactional browse step, which prevents it from promising pricing. It says nothing about return shape, pagination, or result limits for a list endpoint, which is the remaining gap.

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 intent is front-loaded in the first clause, and the four sentences each carry distinct information (what is listed, when to use it, the enquiry-only model, the week-building add-on). The opening sentence is long and em-dash heavy, which slightly blurs the enumeration, but there is no filler or repetition.

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 list tool with no annotations and no output schema, the description supplies the two things an agent would otherwise lack: the scope of the catalog and the enquiry-led, no-charge nature of the interaction. Coverage is solid; only return-format expectations and the routing relationship to the generic list_tours sibling remain unstated.

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 (empty object schema, 0 required), so there is nothing for the description to disambiguate; the baseline for a no-parameter tool is 4. The description correctly describes a parameterless browse operation rather than implying filters that do not 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?

The description uses a clear verb ('List') and a narrowly scoped resource ('Cape Town day experiences Follow On Tours arranges'), then enumerates the actual offerings (city/peninsula tours, Winelands, whale watching, Marine Big 5, shark cage diving, safari, helicopter). That enumeration distinguishes it from the generic sibling list_tours, though it never names that sibling explicitly, so the differentiation is implicit rather than stated.

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?

'Use this for any Cape Town or South Africa enquiry' gives a clear activation context, and 'Follow On Tours also builds a full Cape Town week around these on request' points to the adjacent multi-day case. No explicit exclusions or named alternatives (e.g., when to prefer list_tours or list_golf_trips) are given, so it stops short of a 5.

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