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

With no annotations provided, the description carries full burden for behavioral disclosure. It clearly states the tool computes geometry and photometry but does not render, and lists all output fields (position, size, brightness, moon phase, sky state, etc.). It does not mention authentication, rate limits, or potential side effects, but the absence of annotations and the tool's read-only nature makes this acceptable. The description adds useful context beyond the schema's parameter descriptions.

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 thorough but not overly verbose. It front-loads the purpose and then systematically lists inputs and outputs. Every sentence adds useful information. Minor redundancy could be trimmed (e.g., 'give a place, a moment, an aim...' is clear but slightly wordy). Overall, it is well-structured and concise relative to the tool's complexity.

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 complexity (14 parameters, no output schema), the description is remarkably complete. It explicitly enumerates all expected outputs (pixel positions, sizes, brightness, moon phase, sky state, bodies outside frame, prompt, renderPlan). This compensates for the missing output schema and provides agents with clear expectations. The description also notes edge cases (e.g., 'For "at sunset"...') and clarifies that overlays are annotations, not photoreal.

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 baseline is 3. The description adds value by explaining how parameters contribute to the image prompt (e.g., 'bortle' drives star density, 'overlays' are annotations not photoreal). It also clarifies the relationship between 'max_star_mag' and 'bortle'. This extra context helps agents choose parameters effectively beyond what the schema alone provides.

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 the tool's purpose: computing where visible bodies land in a framed photo of the sky for an image prompt. It specifies inputs (place, moment, aim, lens, size) and outputs (pixel positions, sizes, brightness, etc.). It distinguishes itself from siblings like 'sky_view_sequence' (sequence vs single frame) and 'synthetic_sky_view' (synthetic vs real) through the context of sibling names and the description's focus on real sky geometry.

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 explicit guidance for one common use case: 'For "at sunset", first find the set time with sky_events, then pass it as date.' It also clarifies what the tool does NOT do ('it does NOT render the image'), which helps agents avoid misuse. However, it does not comprehensively list when to use this tool versus all alternative sibling tools, missing some contextual exclusion.

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