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

Annotations already show readOnlyHint=false; the description confirms mutation with 'Mutações' and lists actions. It adds the bulk-execution behavior, but gives no details about what changing a plan affects (billing, current vs next cycle, reversibility, required permissions) and no caveats about potentially destructive actions. No contradiction with annotations.

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?

The description is bloated by enumerating all subscription mutation actions, most of which belong to sibling tools and are irrelevant to this specific endpoint. The useful content ('change_plan', bulk ids) is embedded in a long list with an implementation-detail note, so it is not front-loaded or concise.

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?

Given the schema is minimal, there is no output schema, and the tool is a mutation with nested data, the description is incomplete. It does not clarify the effect of change_plan, the contents of data, response/return behavior, or error conditions; only bulk support is added.

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?

With 0% schema description coverage, the description must compensate for the bare schema. It explains 'id + data' and mentions ids for bulk execution, but leaves 'data' as an opaque object and does not document the 'account' parameter. Critically, it does not specify which fields change_plan expects inside 'data'.

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 identifies the domain ('Mutações em assinaturas Guru') and includes 'change_plan (id + data)' plus '[Flattened action: change_plan]', so the intended operation is inferable. However, the purpose is buried in a long list of unrelated actions (cancel, add_coupon, set_payment_types, etc.) and the description never states in plain terms that this tool changes a plan, making it vague and poorly differentiated.

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?

No guidance is provided about when to use this tool versus the many sibling tools such as guru_subscriptions_write_cancel or guru_subscriptions_write_set_next_offer. The only usage hint is 'Bulk support: accepts ids for batched execution,' which addresses batching but not tool selection.

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