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

Annotations already declare readOnlyHint=true and openWorldHint=false, so the safety profile is covered by structured data rather than the prose. The description adds only that these are "saved" contacts (a modest scope signal) and says nothing about result ordering, pagination, or result-set size limits — meaningful gaps for a list operation.

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, front-loaded with the resource and followed by the optional modifier. Nothing is redundant or padded.

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 read-only tool with one optional parameter and no output schema, the description covers what it returns conceptually and how filtering works. The only shortfall is absent guidance on ordering or how many contacts come back, which matters when listing a potentially large set.

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 single filter parameter is already fully documented in the schema, including case-insensitivity and the name-or-phone match. The description merely restates that same semantics, adding no format hints, examples, or edge-case behavior.

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?

"List the Phone Bud user's saved contacts" gives a specific verb and a clearly scoped resource, so an agent can tell it apart from the agent/campaign/call siblings at a glance. It stops short of explicitly naming what it is not, but no sibling overlaps on contacts, so ambiguity is low.

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 implies the use case (retrieving the user's saved contacts, optionally narrowed by a substring), and the word "Optionally" clarifies the filter is not required. It offers no when-not guidance, no mention of alternatives for searching other resources, and no prerequisites.

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