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

No annotations are provided, so the description carries the full behavioral burden, yet it only implies mutation via 'Add'. It says nothing about required permissions, what happens if the key already exists, whether fields are reversible/deletable, or how pii/shared_with_homeowner affect behavior.

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?

A single front-loaded sentence with no filler. It is efficiently sized, though the efficiency comes at the cost of substance rather than being genuinely tight.

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?

A 9-parameter mutation tool with no annotations and no output schema needs substantially more than one sentence. Missing are required-field guidance (shop_id, key, target, type), key-uniqueness behavior, and the implications of pii and shared_with_homeowner.

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% across 9 parameters, so the description must compensate but does not. The only signal is the list of target entities, which merely restates the target enum; key, type, pii, options, required, and shared_with_homeowner are all left unexplained.

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 (Add) and resource (custom field) plus the target entities, so an agent can tell it is a creation operation. However, it does not distinguish itself from siblings like fields_set or fields_get, leaving the define-vs-set boundary to inference.

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?

No when-to-use guidance is given, and the ambiguous relationship with fields_set (which likely also writes field values) is unaddressed. The agent must guess whether defining a field and setting a field value are the same or different operations.

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