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

Annotations already declare destructiveHint=true, idempotentHint=true and readOnlyHint=false, yet the description adds substantial context beyond them: the 422 pre-write validation on unknown variable names, immediate propagation to the live bot with cache invalidation, and the 409 refusal on resubscribing a contact who blocked the bot. This is exactly the kind of behavioral detail an agent needs before invoking a mutation.

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?

Front-loaded with the action and permission requirement, then ordered by importance: partial-update contract, variable semantics, propagation, status edge cases. Dense and mostly waste-free, though the status paragraph is long enough that it could be tightened slightly.

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 9-parameter mutation with a nested variables object and no output schema, the description covers permissions, idempotency, validation failures, propagation timing, and status edge cases. Nothing material needed to call it correctly is missing.

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 goes further by clarifying that variables keys are NAMES or full folder paths rather than ids, and that ambiguity/unknown names fail with 422. Status semantics are also explained beyond the enum values.

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?

Names a specific verb and resource (update a contact's profile fields and contact-variable values), which cleanly separates it from create_contact, get_contact and list_contacts in the sibling set. The scope of what can be changed is stated up front in the first sentence.

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?

Explains the partial-update contract ('only the fields you pass are changed'), the permission gate (manage_broadcasts), and precisely when status transitions succeed or fail. It does not explicitly name a sibling alternative, but for an update tool the when-to-use case is unambiguous.

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