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

Annotations already declare readOnly/idempotent/non-destructive, but the description adds what they cannot: the response is large (all 82 PEOPLE, ~38 KB) and shrinks to ~5 KB with fields. That payload-size warning is exactly the context an agent needs to avoid blowing its context window, and it is not available anywhere in structured fields.

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?

Two sentences, zero waste. The verb-and-scope statement is front-loaded, then the routing rule, then the size-reducing tip — the most decision-relevant information comes first.

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, yet the description covers the return shape (JSON array), its magnitude, and how to shrink it. Combined with annotations covering safety and the schema covering both parameters, an agent has everything needed to call this 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?

Schema coverage is 100%, so the baseline is 3. The description adds semantics the schema does not: the fields parameter is framed as producing a compact index, with a concrete size consequence (~5 KB vs ~38 KB) and a worked example. That is real added meaning, though the resource enum itself is not elaborated beyond 'resource type.'

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: "Lists every entity of one Star Wars resource type as a JSON array," and scopes the data (Episodes I-VI). It also names the siblings sw_search and sw_get, so an agent can place it apart from the lookup tools 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 the agent: "to find a single entity, prefer sw_search, then sw_get," and gives the condition for staying with this tool (a full-type listing). It also names the escape hatch for a lighter call (pass fields). Both when-to-use and when-to-use-something-else are stated.

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