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

Annotations already declare readOnlyHint=true, idempotentHint=true, and destructiveHint=false, so the safety profile is fully covered by structured data. The description adds only that pagination is supported, without noting default/max page sizes, result caps, ordering, or rate limits. Adequate but thin given the low bar set by annotations.

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 front-loaded sentences with zero filler: the core action comes first, followed by the filter scope and pagination note. Nothing is wasted.

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 list tool with full schema coverage and annotations carrying the safety profile, the description is serviceable. It omits return-shape hints (there is no output schema) such as whether results are paginated envelopes or bare arrays, which would help an agent interpret the response.

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 all five parameters (page, pageSize, tagId, subscribed, apiKey) are already documented in the schema; baseline 3 applies. The description's mention of subscription-status and tag filtering mirrors schema content without adding format or syntax detail.

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 all contacts') plus the filter dimensions and pagination support, so the operation is unambiguous. However, it does not differentiate from the sibling search_contacts, leaving the agent to infer the boundary between listing and searching.

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 'optional filtering by subscription status and tag' implies when the filters are worth using, but there is no explicit when-to-use/when-not guidance and no mention of search_contacts as the alternative for keyword or complex queries. Usage is implied rather than stated.

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