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

No annotations are present, so the description carries the full burden. It discloses computation logic ('time is computed from that spot's own latitude and longitude'), derived fields ('goldenHour', 'blueHour', 'arriveBy'), countdown semantics ('startsIn counts down... alreadyPassedToday'), a unique warning field ('wrongWayRound'), a hard cap ('Returns up to 8'), and an exclusion (weather). This is exemplary transparency.

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 long but dense with necessary nuance; every sentence introduces behavior or guidance that the schema and annotations do not provide. It is not tautological or padded. Minor redundancy exists (multiple mentions of the clock/timing), but the structure is front-loaded and each clause serves a purpose.

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 tool with 4 parameters, no output schema, and no annotations, the description covers the essential behavioral context: return fields, field meanings, timing semantics, edge cases ('alreadyPassedToday'), and a warning against a common mistake ('wrongWayRound'). It even cautions about weather and seasonal availability. This is complete enough for an agent to invoke 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 coverage is 100%, so the baseline is 3. The description adds real value beyond the schema by explaining the implications of `when` ('Pass when: 'sunrise' for the morning side; the default is sunset'), `date` ('to plan ahead... read inBestMonth'), and `query` via examples. It stops short of enumerating every parameter, but its guidance enriches the schema sufficiently.

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 opens with a specific scope: 'Verified East End sunrise and sunset viewpoints' with named venue types. It clearly identifies the tool's job via 'Call this for any sunset, sunrise, golden hour, blue hour, best-views or where-should-we-watch question', differentiating it from sibling tools like beach_info or whats_open_now.

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?

Explicit invocation triggers are given: 'Call this for any sunset, sunrise, golden hour, blue hour...' and even 'call it even when you think you know the spot'. It also states an exclusion: 'There is no weather here, so never promise a clear sky,' giving clear when-not-to-use guidance. No alternative tools are named, but the context is unmistakable.

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