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

Goes well beyond the readOnly=false / destructive=true annotations by disclosing error codes (FD-007, FD-003), the key immutability rule, partial-update semantics, and special handling for system facts (isBlocked/blockReason). This is exactly the kind of mutation-behavior context annotations cannot convey.

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?

Dense but front-loaded: purpose first, then immutable field, then the type-change rule with its error code, then partial-update semantics, then system-fact exceptions. Every sentence carries distinct, actionable information with no filler.

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 mutation tool with a nested valueDomain object and no output schema, the description covers failure modes and field-level constraints well. It stops short of describing the response shape after a successful update, which is a minor gap.

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, but the description adds real meaning: key immutability, the conditional nature of type changes, and which fields system facts accept versus ignore. That is useful value on top of an already well-documented schema.

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 fact definition'), which is unambiguous against siblings like lexq_facts_create or lexq_facts_delete. It does not explicitly name a sibling to distinguish from, but the name and verb make the intent 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?

Gives concrete preconditions that determine whether the call will succeed: type changes require no referencing rule, deleted-group rules don't count, and only sent fields change. It lacks explicit routing to alternatives, but the conditional constraints effectively tell the agent when and how to invoke it.

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