plc_create_variable

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

Annotations already establish write, non-destructive, non-idempotent, closed-world behavior. The description adds genuine value by disclosing that changes are staged rather than applied immediately and that case-insensitive name collisions are rejected, but it stops short of explaining what happens on rejection, what permissions are needed, or that a commit step is required to persist the declaration.

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 short, front-loaded sentences with no filler; the staging behavior leads and the collision rule follows. The terseness comes at the cost of omitted workflow context rather than wasted wording.

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 six-parameter mutation tool with five required parameters, an output schema, and near-zero schema coverage, the description is thin. It omits the transaction lifecycle (begin, stage, commit), the role of expected_revision, and what a rejection looks like, leaving key invocation details undocumented.

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 only 17%, so the description needs to carry most of the parameter burden. It obliquely maps 'existing global or local VAR group' to table_id and implies name and data_type meaning, but says nothing about transaction_id, initial_value, or how expected_revision participates in optimistic concurrency.

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?

The description names a specific verb and resource: staging a variable declaration into an existing global or local VAR group. That is clearly distinct from sibling operations like plc_rename_variable or plc_update_variable, though it does not explicitly call out those siblings as alternatives.

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?

Usage is only implied. The phrase 'existing ... VAR group' signals a prerequisite that the target group must already exist, and 'Stage' hints at a transaction-based workflow, but the description never states when to choose this over plc_update_variable or plc_rename_variable, nor that a transaction and commit are involved.

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