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

Annotations already cover the safety profile (readOnly, idempotent, non-destructive, closed-world), so the bar is lower. The description still adds meaningful behavior beyond them: results are merged 'soonest first,' each venue carries a distance in km, and an ambiguous suburb produces candidate states requiring a follow-up call. That is useful operational context.

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?

Three dense sentences with no filler; the core behavior and the required-input caveat are front-loaded. It is compact for the amount of nuance conveyed, though the last sentence is somewhat long.

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?

An output schema exists, so return values need not be spelled out, and the annotations carry the safety profile. The description still supplies the ordering, distance unit, and the recovery flow for ambiguous suburbs, leaving nothing an agent needs to invoke it correctly.

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 all six parameters are already documented in the schema, including defaults, caps, and formats. The description reinforces the required nature of 'near' but adds no syntax or format detail beyond what the schema provides, so the baseline 3 applies.

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 specific verb and resource: 'Upcoming sessions of one course across the venues closest to a postcode or suburb,' with the added ordering and distance semantics. It is clear what the tool returns. It does not, however, differentiate itself from the sibling search_sessions, which the agent must disambiguate on its own.

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 concrete context: 'near is required: this server can't tell where the person is, so ask them for their postcode or suburb,' and describes the retry path when a suburb is ambiguous. That is real when-to-use guidance for a required input. It stops short of stating when to prefer this over search_sessions.

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