Metafields Update

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

Annotations already declare non-read-only, idempotent, non-destructive, open-world behavior, so the description is not carrying the safety burden alone. It does add genuinely useful non-annotated context: the PUT route, the required OAuth scope mapped to owner_resource types, and the API version. It omits the key behavioral question for an update tool — whether omitted fields are left untouched or cleared — and says nothing about the metafield value type constraint.

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?

Four short, front-loaded lines with no filler — operation first, then route, then auth, then version. Every line is factual, though the scope enumeration is verbose relative to its decision value.

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 4-parameter mutation with full schema coverage, no output schema, and annotations covering the safety profile, this is close to sufficient: identity, route, auth scope and API version are all present. The remaining gap is update semantics (partial vs. replace, type validation of `value`), which matters for metafields specifically.

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 100%, so the schema already documents id, value, description and additional_fields; the baseline of 3 applies. The description adds nothing about parameter behavior beyond showing {id} in the path, and notably does not warn that `value` must conform to the metafield definition's 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 ('Update a metafield') plus the exact HTTP route, so the agent knows precisely what operation this performs. It does not name or contrast the sibling metafields_create / metafields_get / metafields_delete tools, but the verb makes the distinction obvious.

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?

There is no guidance on when to choose this over metafields_create (upsert semantics?) or when a metafield must be deleted and recreated. The scope line describes an authorization prerequisite rather than a usage decision, and no conditions or exclusions are given.

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