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

Annotations already cover readOnlyHint=false, destructiveHint=false and openWorldHint=true, but the description adds meaningful context beyond them: the default per-call confirmation, the ability to disable it, the fact that the activity 'reaches other people,' and the requirement for a Cotlet API key with access to this app. This is solid behavioral disclosure for a mutation tool.

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 core purpose is front-loaded, but the second sentence largely restates the first ('Add ... to a contact and assign it to a user' vs 'Adds an activity ... to a contact and assigns it to a user'), which is redundant. The confirmation and auth sentences earn their place, but the opening duplication costs it.

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 mutation tool with annotations present and no output schema, the description covers the important gaps: confirmation behavior, external visibility, and API key requirements. It is largely complete, though it does not clarify how it relates to sibling activity tools.

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 100%, so all five parameters (contact_id, activity_type, due_at, reference, assigned_to) are already documented in the schema. The description mentions assignment to a user but adds no syntax, format, or default detail beyond what the schema provides, so the baseline of 3 applies.

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 states a specific verb and resource: 'Add a follow-up activity to a contact and assign it to a user,' and clarifies it is an 'activity of one of your Activity Types' shown in the Activity List. This lets an agent distinguish it from marketsharp_add_note and marketsharp_complete_activity reasonably well. It does not explicitly name those siblings, so it falls short of a 5.

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?

It gives operational guidance ('By default you confirm each call; you can switch that off') and a pre-call confirmation requirement ('confirm with the user before each call'), which is useful. However, it never states when to use this tool versus alternatives like marketsharp_add_note or marketsharp_schedule_appointment, so usage context is only implied.

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