Update Assignment Group

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

Annotations declare idempotentHint and destructiveHint, and the description reinforces idempotency with partial-update semantics ('anything omitted keeps its current value'). It goes well past the annotations by disclosing failure modes: Canvas rejects a drop rule exceeding active assignment count, and returns an authorization (not validation) error for `group_weight`/`rules` changes when assignments sit in a closed grading period, except for account admins. That is exactly the kind of behavioral context annotations cannot carry.

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?

Purpose and the create-vs-update distinction are front-loaded, which is correct. The single paragraph becomes dense and clause-heavy once it reaches the grading-period and drop-rule caveats, costing a bit of scannability, though nearly every sentence carries non-redundant 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 a destructive, nested-object mutation with no output schema, the description covers return value, partial-update semantics, prerequisites, permissions, and two specific error conditions. Nothing an agent needs in order to call this safely appears to be 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, but the description adds real meaning: `group_weight` is a percent of final grade that only matters under weighted grading, and `rules`/`never_drop` exempt specific assignments from drops. It does not touch `position`, `sis_source_id`, or `name`, so it stops short of a full 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 and resource ('Update an existing assignment group in a course') plus the return value, and explicitly distinguishes itself from the sibling `create_assignment_group` by contrasting partial update vs. always-new-group. An agent can route between the two without opening either schema.

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?

Names the concrete use case ('repair a weighted gradebook'), the prerequisite read step (`list_assignment_groups` for current values and ID), the permission needed, and the alternative to avoid (`create_assignment_group`). It even flags that `group_weight` is inert unless the course is weighted and points at `update_course` to enable that — genuine when/when-not guidance.

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