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

Annotations already declare readOnly=false / destructive=false / idempotent=false, so the safety bar is lower. The description still adds real behavior beyond them: CRUD endpoints activate immediately upon creation (a live side effect), and the key is a unique 3-char UPPERCASE constraint. It does not mention duplicate-key errors or naming collisions, so not full marks.

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?

Three tight sentences, front-loaded with the action, then the side effect, then the field-bulk tip. Nothing is wasted, though the key-format sentence duplicates the schema param description rather than adding new information.

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 an 8-parameter creation tool with no output schema, the description covers purpose, side effect, and the highest-leverage parameter (fields). Undescribed in the prose are `methods`, project_id fallback, and the returned shape, but those are documented in the schema. Adequate overall, with modest gaps.

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 genuinely adds meaning on the `fields` argument by framing it as a single bulk request that replaces N create_field calls, and pins the key format constraint. The key restatement is redundant with the schema, hence 4 rather than 5.

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 + resource + scope: 'Define a new data entity under a project.' It also catches the edge case by pointing at the internal alternative ('instead of a create_field per field'), which helps disambiguate from siblings. It does not, however, explicitly contrast with update_entity/delete_entity, so the sibling differentiation is partial.

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?

Gives a clear situation for use (defining a new entity) and explicitly names a routing decision: use the bulk `fields` argument rather than calling create_field repeatedly. There are no explicit 'when not to use' exclusions (e.g. use update_entity to modify an existing one), so it stops short of a 5.

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