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

Annotations already establish the safety profile (read-only, idempotent, non-destructive, closed-world), and the description adds real behavioral context: a 512-orbit ceiling, a 4-million CPU-step budget, 'explicit stops,' and result-interpretation limits. It stops short of describing how truncation or 'explicit stops' surface in the response, which the output schema presumably covers.

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 tight sentences, front-loaded with the operation and its budget, with no filler. The interpretation caveats are dense but arguably necessary given the tool's misuse potential; nothing reads as padding.

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-value explanation is not strictly required, yet the description usefully names the outputs anyway. The real gap is the 12 undocumented parameters and the absence of any indication of default values (e.g., Jupiter semi-major, mass ratio) or how the 512-orbit cap interacts with a 64×64 grid request.

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 0% across 12 parameters, so the description must carry the load, and it only partially does: 'up to 512 initial orbits' maps to n_a×n_e and 'at most 4 million reserved CPU steps' maps to max_work_units. Units and meaning for mass_ratio, duration_yr, steps_per_year, initial_phase_deg, jupiter_semi_major_au, and the a/e bounds are left entirely to bounds inference.

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?

States a specific verb and resource ('Survey ... initial orbits') and pins the physical model ('planar circular Sun–Jupiter'), which is far more than the name conveys. It does not explicitly distinguish itself from near-neighbor siblings such as compute_orbit or propagate_uncertainty, so it falls short of a 5.

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?

Usage is implied rather than stated: this is a stability survey tool, and 'Direct-only' signals an invocation constraint, but no when/when-not or sibling alternative is named. The interpretive caveats ('Bands do not prove chaos or stability; radial overlap is not an encounter') guide result reading, not tool selection.

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