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

Annotations already declare readOnly=false, idempotent=true, destructive=false and openWorld=false. The description adds real value beyond them: the consent guardrail and the fact that every resulting email carries an unsubscribe link, which tells the agent the consequence of the write is user-reversible. It stops short of describing error behaviour (e.g. duplicate emails) despite 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?

Two short sentences, zero filler, with the consent constraint placed immediately after the action so the agent reads the guardrail before acting. Nothing is redundant with the title or schema.

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 simple two-parameter, non-destructive, idempotent tool with no output schema, the description covers the action, the consent precondition and the user-facing consequence. Only marginal gaps remain (duplicate handling, invalid-email behaviour), which the annotations partly mitigate.

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%, so the description carries the burden. It does clarify the meaning of 'consent' (the person asked, and it must be true), which the bare schema const does not explain, but it adds nothing about the 'email' parameter beyond 'an email'. Baseline 3 for a two-param tool with no schema prose.

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 pairs a specific verb ('Subscribe') with a specific resource ('an email to new-tool announcements'), so the action is unambiguous. It does not explicitly distinguish itself from any sibling (e.g. feedback or request_tool), but the function is distinct enough that routing confusion is unlikely.

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?

'only when the person asks for them (consent:true)' is an explicit precondition that tells the agent when to call this tool and, by implication, when not to. No alternative tool is named, but there is no comparable sibling offering subscription, so this is sufficient context.

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