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

Annotations already declare readOnlyHint=true, so the safety profile is covered. The description adds the upstream endpoint (GET /activities) and filtermode semantics, but says nothing about result volume, pagination defaults, or ordering determinism — details that matter for a list endpoint and are only partly covered by the schema.

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?

Front-loaded with the verb/resource/scope, then filtermode, then a single concrete example. The example JSON is bulky but earns its place by showing operator syntax. No filler sentences.

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 read-only list tool with full schema coverage and annotations carrying the safety signal, this covers what the agent needs to invoke correctly. With no output schema, it still leaves the returned shape and pagination behavior implicit rather than stated.

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 a 3 is the baseline. The description exceeds it by explaining filtermode's three values and by demonstrating a non-obvious filter construction (time_status_eq + starts_at_lt + ends_at_gteq with an array participant key) that the schema's generic filters examples do not illustrate.

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 (List) and resource (activities), and goes further by enumerating what an activity is — calls, meetings, tasks, notes — and the entities they attach to (members, opportunities, projects). That scope cleanly separates it from the other list_* siblings, though it never names an alternative tool to route against.

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?

Gives real usage signal: the filtermode values (pending/completed/all) and a worked example for the common 'one person's busy time in a window' query, which tells the agent how to combine time_status with starts_at/ends_at and participants_member_id. It stops short of explicit when-not-to-use-this or naming a competing tool.

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