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

Annotations already cover the safety profile (readOnly, idempotent, non-destructive), so the description adds real value by disclosing ordering, page size, the meaning of meta.count, and precisely which records are counted (those with an email, phone, or identifier). The caveat about records with only a name not being counted is useful behavioral nuance.

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?

Front-loads the core action and is generally efficient, but the closing advice about wording ("say 'contacts with contact details'") is somewhat wordy for a definition. Most sentences earn their place.

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?

With no output schema, the description does well to explain the count field and ordering. It leaves minor gaps: it never mentions the fields parameter or how this list differs from search_contacts, but overall it is adequate for correct invocation.

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 both parameters (page, fields) are already documented in the schema. The description echoes the page size (15) but adds no syntax or format detail beyond the schema, so the baseline of 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?

States a specific verb and resource ("List the contacts of this account") and adds ordering ("most recently active first") and page size ("15 per page"). It is clear what the tool does, though it never names a sibling like search_contacts or get_contact to sharpen differentiation.

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?

Provides one concrete usage scenario: use meta.count to answer "how many contacts do I have" without paging. However, it gives no guidance on when to use this list tool versus search_contacts, contact_filter, or get_contact for single-record lookups.

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