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

Annotations already declare destructiveHint=true and idempotentHint=true, so the safety profile is partly covered. The description adds genuinely new behavioral context: the operation is irreversible ('Cannot be undone'), the required authorization (manage token), and the precise blast radius (annotation gone, traffic data preserved). It stops short of describing error behavior on repeat calls, which matters given the idempotent hint.

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 irreversible action and its scope limitation, followed by the prerequisite and the endpoint. No filler; every clause carries information.

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 two-parameter destructive tool with no output schema, the description covers purpose, irreversibility, scope of effect, and auth requirement – everything an agent needs to decide and invoke correctly.

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% – both parameters carry their own descriptions, formats, and discovery hints (fathom_list_sites, fathom_list_milestones). The description only restates them in the REST path template, adding no meaning beyond the schema, 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?

States a specific verb and resource ('Permanently delete a milestone') and immediately narrows scope by clarifying that only the annotation is removed while traffic data is untouched. This clearly distinguishes it from fathom_update_milestone, fathom_create_milestone, and fathom_get_milestone.

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?

The description establishes prerequisites ('Needs a manage token for the site') and the consequence of use, which implies when it is appropriate, but it never names an alternative or states an explicit when-not-to-use condition (e.g. use update_milestone to disable tracking instead of deleting). Usage is inferable but not spelled out.

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