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

With no annotations provided, the description carries the full burden and does so well: it discloses the authorization requirement (staff + manage), the destructive side effect (queued calls to the number are canceled), the scope of effect (no workspace can call it), and the customer-visible semantics. That is rich behavioral context beyond 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?

Three dense sentences, front-loaded with the access constraint, then the action, then the effect and visibility. Every sentence adds distinct information with no waste.

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?

No output schema and no annotations, so the description must stand alone; it covers auth, effect, and visibility, which is most of what an agent needs for a mutation. It omits return shape and whether the action is reversible/idempotent, but the sibling platform_blocklist_remove implies reversibility.

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 0% for two parameters. The description implies a 'number' is added but gives no format guidance (the schema pattern is undocumented), and it says nothing about the required 'reason' parameter. It fails to compensate for the coverage gap.

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: 'Add a number to the platform do-not-call list.' The 'add' verb plus the 'platform do-not-call list' resource distinguishes it from the sibling platform_blocklist_remove and platform_blocklist_list without needing to name them.

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 clear preconditions — 'Platform staff only (account session)' and 'Requires manage' — which tell the agent who may call it. It does not explicitly name an alternative tool or state when-not-to-use, so it falls short of a 5.

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