count_activities

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

Annotations already declare readOnlyHint=true, openWorldHint=true and destructiveHint=false, so the safety profile is covered and the description's 'read-only' restates it. It adds account scoping ('current user account') but says nothing about rate limits, pagination, or what happens with zero activities.

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?

Two short sentences, front-loaded with the purpose — good. But the trailing parenthetical is boilerplate carried over from date-scoped siblings and does not earn its place on a zero-parameter tool.

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 value explanation is unnecessary, and the purpose is stated. However, the dangling date-format remark is a leftover that creates ambiguity about whether this tool accepts date filters, which the description should not leave open.

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 zero parameters the baseline is 4, but the description injects '(Dates are YYYY-MM-DD.)' even though the schema has no properties, which is confusing and may lead an agent to believe date arguments exist. That spurious note drags it below the clean baseline.

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 ('Return total number of activities') and scopes it to the current user account. This is clearly distinguishable from the listing siblings like get_activities or get_activities_by_date, though it never names them explicitly.

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?

Usage is only implied: the phrase 'total number' signals a count-only use case versus the list-returning get_activities sibling. There is no explicit when-to-use, when-not-to-use, or alternative named.

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