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

Annotations already declare readOnlyHint=true, openWorldHint=true, idempotentHint=true, and destructiveHint=false. The description adds valuable behavioral context beyond these: it states 'No auth required; free commercial use', explains output semantics (altitude negative below horizon, azimuth compass directions), and defines golden hour. This helps the agent understand the nature of the data and response, though it doesn't cover potential rate limits or response structure (which is partly covered by the output schema).

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 moderately sized but each sentence adds genuine value: core output, explanation of key terms (altitude, azimuth, golden hour), additional outputs, use cases, and auth/licensing. It is front-loaded with the main functionality and avoids fluff. A slightly more compact structure could be achieved, but it is well-organized and not overly verbose.

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?

Given the tool's moderate complexity (5 parameters, output schema exists), the description is quite complete. It explains the key outputs, defines important terms, lists use cases, and notes the free commercial use. The presence of an output schema means return values need not be described. Minor gaps like handling of polar regions or edge cases are not critical for an agent to invoke the tool 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?

The input schema has 100% coverage with each parameter (lat, lng, date, timezone, time_format) having a clear description. The tool description itself does not add additional parameter-specific semantics beyond what the schema provides, such as explaining the interaction between date and timezone or the effect of time_format. However, the schema is thorough, so the description doesn't need to compensate. Baseline of 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 description clearly states a specific verb ('Get') and resource ('sun position (altitude and azimuth), sunrise/sunset compass bearings, golden hour window, and solar noon time') and includes additional details like dawn, dusk, and day length. It is concise and unambiguous about what the tool does, and the title adds distinct context ('Sun Position & Golden Hour') that differentiates it from other astronomy-related siblings.

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 description provides implied usage context by listing use cases ('solar panel orientation, photography planning, outdoor event scheduling, and navigation'), but it does not explicitly state when to use this tool versus alternative astronomy tools (e.g., sunrisesunset.astronomy.daily or moon.phase). No exclusions or alternative routing are provided, leaving some ambiguity for an agent deciding between siblings.

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