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

Goes well beyond annotations by disclosing that no email is sent, double opt-in is not offered, consent responsibility lies with the user, and that the server never auto-subscribes. Also explains the overwrite replacement behavior and the failure-on-existing-lead condition — none of which the annotations (destructiveHint, idempotentHint) convey.

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?

Well-structured and front-loaded with the WRITE marker and core action, followed by critical behavioral caveats. Every sentence carries distinct information (default, consent, failure mode, overwrite semantics) with no filler.

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 9-param write tool with no output schema and nested objects, the description covers the safety-critical behaviors (consent, overwrite destruction, no email sent) that the annotations alone would not fully clarify. Nothing essential is missing.

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 78%, so the schema already documents most parameters including subscribed, overwrite_existing, fields, ip_address, and tags. The description reinforces the subscribed default and overwrite semantics but adds little syntax or format detail beyond what the schema provides.

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 ('add a lead (contact) to the brand') and clearly contrasts with the sibling mailbluster_update_lead by establishing creation semantics. The WRITE: prefix front-loads the mutation nature.

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?

Explicitly names when to set subscribed=true vs. false, and gives the overwrite_existing=true condition as the alternative path when the lead already exists. This is explicit when/when-not guidance rather than implied usage.

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