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

Annotations already declare read-only, idempotent, open-world behavior, so the bar is lower. The description still adds real value by disclosing the underlying data source (one row per planet in `pscomppars`) and the return contents (unit and query date), which the annotations cannot convey.

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?

Front-loads the core purpose, then adds the source distinction, usage trigger, filter example, and return format in tight, non-redundant sentences. Every clause earns its place.

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?

No output schema exists, but the description compensates by stating it returns the unit and query date. For a simple count tool with one optional parameter this is nearly complete; a note on edge cases (e.g. zero-result or ordering) would be the only remaining gap.

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 single `query` parameter is already fully documented including its example. The description adds the semantic framing that the filter 'narrows the count' but otherwise repeats the same example the schema provides, so baseline 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?

States a specific verb (count) and resource (confirmed exoplanets), and distinguishes the data source from alternatives by naming the composite `pscomppars` table versus the per-solution `ps` table. An agent can differentiate it from the sibling `planets` retrieval tool without opening a schema.

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?

Explicitly routes 'how many confirmed exoplanets' questions to this tool and clarifies the table semantics vs `ps`. It gives clear context but stops short of naming the sibling tools (e.g. `planets`, `kepler_candidates`) it should be preferred over, so the when-not guidance is only implicit.

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