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

Annotations already establish that this is a safe, read-only, idempotent, closed-world computation. The description adds genuine behavioral context beyond that: the two-body idealization, that time is measured from periapsis, that distances are in AU, and an explicit scope limitation. It does not, however, describe return values or accuracy bounds.

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 short sentences, zero filler, with the core action front-loaded and the disambiguating caveat placed last. Every sentence carries distinct information (purpose, units/frame, scope limit).

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?

With no output schema and no parameter descriptions, the description should carry more burden. It covers the physical setup and units but never says what the computation returns (position, velocity, orbital elements) or how results should be interpreted, which is a real gap for an agent invoking it blind.

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%, so the description must compensate. It supplies units and reference frame (AU for distances, time from periapsis) that the bare schema lacks, covering elapsed_days and semi_major_au implicitly. It says nothing about the eccentricity parameter or the meaning of the numeric bounds.

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 ("Compute an ideal elliptical orbit") plus the physical model (one solar mass, two-body). It implicitly separates itself from check_ephemeris by declaring it is not a real ephemeris, but it does not name or contrast with any sibling tool directly.

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 closing caveat ("not a real celestial ephemeris") implies when not to rely on this tool for real-world ephemeris work, which routes the agent away from it. However, there is no explicit when-to-use statement or named alternative, so usage is only implied.

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