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

Annotations already declare readOnlyHint, idempotentHint, openWorldHint and destructiveHint=false. The description still adds two pieces of non-annotation context an agent needs: it requires a master API key, and it costs $0.012 per successful request, which affects invocation decisions.

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 functional sentence is short and front-loaded, with the auth requirement following immediately. The embedded pricing comment block is boilerplate that consumes roughly half the text but is at least clearly demarcated.

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?

An output schema exists, so return values need not be explained, and the single-parameter read operation is otherwise straightforward. Still, the description never characterizes the scope of 'stats' or positions the tool against its emailer siblings, leaving a gap for an agent choosing among many get_/post_ apollo tools.

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% with a single, fully-documented 'id' parameter, so the baseline is 3. The phrase 'specific outreach email' adds only light framing and no format, source, or ID-resolution guidance beyond the schema.

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+resource ('Check email stats for a specific outreach email'), which is clear enough to act on. It does not, however, differentiate itself from the sibling get_apollo_emailer_messages_search or explain what 'stats' actually covers, and the tool name's 'activities' is not reflected in the description.

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?

No when-to-use or when-not-to-use guidance is given, and no alternative is named despite several emailer-related siblings. The only conditional information is the auth prerequisite ('Requires a master API key').

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