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

Annotations only declare readOnly=false, openWorld=true, idempotent=false, destructive=false; the description adds what those hints cannot: exactly one email from a named sender, a consent checkpoint before sending, hard privacy exclusions (no last names, schools, phone numbers, health/disability/accommodation data, other children), and a data-retention fact ('request is deleted in 7 days if the parent doesn't confirm'). It also discloses the response is identical regardless of whether the parent already has an account, which prevents the agent from probing for account existence.

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 purpose and sender before the usage rules and privacy constraints, and almost every sentence is actionable. Minor cost: the privacy exclusions are stated twice (once for the email, once for note), which partially duplicates what the schema's note and childFirstName descriptions already say.

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-parameter mutation with nested objects and an open-world side effect (a real email), the description covers purpose, consent, recipient handling, privacy limits, sibling routing, and expected reply text. An output schema exists, and the description still shows the canonical reply string, which is more than enough 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% and each field already carries its own constraints, enums, and ranges, so the schema does the heavy lifting. The description reinforces the collection policy ('Ask only for the child's first name') and repeats the note restrictions rather than adding new field-level meaning. Baseline 3 is appropriate for fully documented parameters.

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, channel, sender, and payload: 'Sends one email from SATCoach (hello@satcoach.ai) to a parent, with a link to set up SATCoach for their child', then enumerates the carried data. It also distinguishes itself from both siblings by name (about_satcoach, skill_check), so an agent can route correctly without opening a schema.

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?

Gives an explicit gating condition ('only when a parent wants SAT help for their child and wants SATCoach to follow up'), a required pre-call workflow (show the parent exactly what will be sent, get a yes, then set consent to true), and explicit exclusions with the alternative tool for each ('student asks for themselves', 'use about_satcoach', 'use skill_check'). Nothing is left to inference.

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