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

Annotations already declare readOnlyHint=true and destructiveHint=false, so safety is covered structurally. The description adds genuine context beyond them: case-insensitive search matching and the auth prerequisite ('Cotlet API key with access to this app'). It does not discuss pagination behavior, though the cursor param covers that in 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?

The description is short and front-loads the resource ('Your Address Book') before the mechanics. The 'Paperless Post: Your Address Book:' framing lightly duplicates the title, but every other sentence (return content, use case, matching behavior, auth) 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 read-only list tool with no output schema and full schema coverage, the description covers what is returned, search behavior, and the API-key requirement. An agent has enough to call it correctly; only pagination nuance (from cursor) is left to the schema.

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%, so the baseline is 3. The description adds semantics the schema lacks by noting that search matching is case insensitive, which tells the agent how matching behaves rather than just that a search field exists.

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 states a specific verb and resource ('Returns the contacts saved in your Address Book') and clarifies these are reusable address-book people, implicitly distinguishing them from per-event siblings like paperless-post_list_guests. It stops short of naming that sibling explicitly, so it is clear but not fully sibling-differentiated.

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 phrase 'so your agent can add known people to a guest list without a file' gives an implied use context, but there is no explicit when-to-use/when-not statement and no named alternative (e.g., list_guests for event attendees). Usage is inferable rather than stated.

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