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

With only readOnlyHint=true in annotations and no output schema, the description carries the return-value burden and does so: it discloses that the response contains title, version number, and a template boolean. It also reveals the backing mechanism ('GraphQL query: cast'), which helps an agent reason about failure modes, though it says nothing about behavior for an invalid or missing eid.

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 compact sentences with the fetch semantics and return fields front-loaded, followed by the chaining instruction. Nothing is repeated from the schema or annotations, and 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?

For a single-parameter read with no output schema, the description supplies the essentials: what is fetched, what comes back, and where the result is consumed next. It could be marginally more complete by noting error behavior for a nonexistent eid, but nothing an agent needs to call it correctly is missing.

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% for the single eid parameter, so the baseline is 3; the description goes slightly beyond by identifying the eid as the cast's identifier and, crucially, explaining that the returned eid is what feeds cast_eid on anvil_fill_pdf. No format or validation details for the eid itself are added.

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 (Fetch) and resource (a cast / Anvil PDF template) and disambiguates the term 'cast' for an agent unfamiliar with Anvil's vocabulary. It also previews the returned fields (title, version number, template flag), so it is distinguishable from sibling getters like anvil_get_weld or anvil_get_etch_packet.

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 forward: 'Use the returned eid as the cast_eid for anvil_fill_pdf,' naming the concrete sibling and parameter to chain into. It does not state when not to use this tool or contrast it with the other anvil_get_* siblings, so it stops short of full when/when-not guidance.

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