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

Annotations already declare readOnlyHint=false and destructiveHint=true, so "WRITE, destructive" largely restates structured data. The one piece of added value is the semantic consequence that the contact stops appearing in caller ID, plus the underlying REST endpoint; reversibility and permission requirements are still unstated.

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 clauses, front-loaded with the write/destructive classification before the action and endpoint. Nothing is padded; every element 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 destructive, no-output-schema tool the description covers the action, scope, effect, and endpoint, and the schema's confirm field documents the approval gate. Only irreversibility and permission context are missing, which is a minor gap.

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 33% – only confirm is documented in the schema. The description and the embedded path template (DELETE /phonebooks/{id}/contacts/{contactId}) do signal that phonebookId and contactId identify the parent phonebook and target contact, partially compensating, but no format or sourcing details are given.

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 (delete), resource (one contact in a phonebook), and scope (single contact), which clearly separates it from the get_/list_/save_phonebook_contact siblings. It doesn't explicitly name an alternative, but the verb+resource combination is unambiguous.

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 by the verb; the description adds the consequence ("it stops showing in caller ID") but no explicit when-to-use/when-not or routing to alternatives such as save_phonebook_contact. An agent can infer intent but gets no guidance on preconditions beyond what the schema's confirm field states.

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