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

Annotations already establish that this is a non-read-only, non-destructive, non-idempotent, closed-world mutation, so the safety profile is covered. The description adds genuinely new behavior: 'Top protects booked tickets' and 'lowering a tier never removes protection' explain side effects the annotations cannot express. It stops short of disclosing whether a change notifies the user, whether notes overwrite existing notes, or why the operation is not idempotent.

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 short sentences, front-loaded with the action and the enum, followed by the protection caveat and the negative scoping statement. Nothing is padded, though enumerating all six tier values duplicates the schema enum and spends words that could have described 'notes'.

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?

An output schema exists, so return values need not be explained, and the mutation's safety profile is in annotations. Still, for a three-parameter write tool the description leaves the 'notes' parameter and the meaning of 'existing rules' entirely opaque, which is a meaningful gap for correct invocation.

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 0%, so the description carries the full burden, yet it only restates the tier enum values that the schema already lists explicitly. The 'notes' parameter (maxLength 4000) is never mentioned — an agent has no idea what notes are for or whether they replace or append. 'filmId' is likewise unexplained beyond its regex pattern.

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 verb 'Set' plus the enumerated tier values make the operation recognizable, and the title supplies the missing object ('a movie's planner tier') that the description itself leaves implicit. It also differentiates from request_booking by stating 'Does not create a booking request', so an agent can separate it from the booking siblings. The only weakness is that the description alone never names the resource being modified.

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?

There is one explicit exclusion ('Does not create a booking request') and a rule about protection semantics, which implies usage context. However, 'using existing rules' is undefined, and there is no guidance on when to choose this versus set_reminder, request_booking, or set_format_preference among the many siblings. Usage is implied rather than stated.

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