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

Annotations only declare the safety profile (not read-only, non-destructive, idempotent, open-world); the description adds substantive behavior beyond them: the key is validated against Granola before storage, kept only if it works, encrypted at rest, never returned in responses, and only the last four characters are retained in the audit log. These are exactly the operational facts an agent cannot get from structured fields.

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?

One dense but well front-loaded sentence with the core action first, then the validation/storage guarantees, then the permission boundary. The parenthetical explanation of why the key matters earns its place; the phrasing is slightly compressed but not wasteful.

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?

There is no output schema, so the description correctly covers the return behavior ('never answered back', audit keeps only last four characters) as well as validation, storage, encryption and the owner-only restriction. Nothing needed to invoke a one-parameter save tool correctly 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 100% for the single 'key' parameter and the description adds only the same format hint ('grn_…') already present in the schema, so the baseline of 3 for schema-covered params 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 (save) and resource (the workspace's Granola API key) and immediately scopes ownership ('its own'), which distinguishes it from make_an_api_key, list_api_keys, revoke_an_api_key and remove_the_granola_key among the siblings.

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?

It conveys the consequence of not having the key ('without them Tommo writes no letter after a call') and the access restriction ('For the owner only'), which implies when this action matters, but it never explicitly names an alternative (e.g. remove_the_granola_key) or states prerequisites for when to call it versus a general API-key tool.

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