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

Annotations already declare readOnlyHint=true, destructiveHint=false and openWorldHint=false, so the safety profile is covered. The only added behavioral detail is that the response includes the record types a field is placed on, which is modest value given an output schema exists.

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 zero filler. It is efficient, though the terseness leaves gaps that a second short clause about lookup mode could have closed.

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?

The output schema covers return values and annotations cover safety, so the description needn't repeat those. However, with zero required parameters and three lookup inputs, an agent still cannot tell from the description how to identify the field, which is a material gap for a nested-object schema.

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?

The schema is only 67% described and nests id/ref/companyId wrappers, yet the description says nothing about the two lookup modes (by UUID vs by ref key/owner) or which of the three optional parameters is needed. It adds no meaning beyond the schema's own field names.

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?

Specific verb ('Read') plus resource ('one field definition') and it also states the payload includes the record types the field is placed on. This distinguishes it from the list sibling schema_get_list_field_definitions, though it doesn't name that sibling explicitly.

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?

'Read one' implies a single-entity fetch versus the plural list tool, so usage is inferable but never stated. There are no conditions, prerequisites, or explicit alternative named.

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