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

readOnlyHint=true already declares the safety profile, so the description only needs to add context. It does disclose the page size ('100 per page') and the shape of each record, but says nothing about total counts, pagination metadata, or rate limits.

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?

One front-loaded sentence with no filler; the resource, returned fields, and page size all appear immediately.

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 read tool with a fully documented schema and a readOnly annotation, the description covers purpose, returned fields, and page size—enough to call it correctly. It could mention that pagination continues via next_start, but the schema already says so.

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 100%, so limit and start (including the next_start chaining tip) are already fully documented in the schema. The description's '100 per page' largely restates the limit maximum rather than adding new parameter meaning, so the baseline 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?

The description gives a specific verb and resource ('List contacts in the account') and even enumerates the fields returned (name, phone, email, groups). It does not distinguish itself from close siblings such as list_contacts_in_group, list_do_not_contacts, or get_contact, so it falls short of a 5.

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: this appears to be the general 'list all contacts in the account' call, which implicitly excludes group-scoped or do-not-contact listings, but the description never says so or names those alternatives. Nothing states prerequisites or when a single get_contact lookup would be preferable.

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