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

With no annotations, the description carries the behavioral burden and does well: it discloses PATCH-style semantics, the required permission, and an error condition (404). The only notable omission is the success response shape.

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 core behavior, then permission and error behavior. No filler or repetition of schema field names.

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 simple flat schema and low parameter count, the description covers the essentials for a correct call: action, partial-update semantics, required permission, and id-related error behavior. It would be more complete if it stated the success response, but the tool is simple enough that this 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. The description adds meaningful parameter context beyond the schema: only sent fields change, so optional body fields act as a partial update set, and the 404 clause clarifies that activity_id must be present and belong to the organization.

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?

Begins with a specific action and resource: 'Updates one activity in the tenant CRM.' The 'one activity' qualifier plus the partial-update phrase clearly differentiates it from create/delete/get/list siblings, and 'tenant' distinguishes it from the platform-scoped update sibling.

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?

Clear context is provided: it is for modifying an existing activity, needs crm:write, and gives a 404 signal when the id is missing or foreign. It stops short of explicitly naming alternatives or when-not-to-use, so it misses a 5.

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