refresh_session_cookie

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

With no annotations, the description carries the full load and does well: it discloses the side effect (the stored cookie is replaced), the required credentials (BTWB_EMAIL plus a Keychain password under service btwb-password), and the implicit auth/network dependency. It stops short of describing failure behavior or whether old sessions are invalidated, so it is strong but not exhaustive.

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?

Three sentences, front-loaded with the action and immediately followed by the 'you usually don't need this' caveat. The credential detail is necessary; the README pointer is slightly expendable but reasonable for a rare maintenance tool.

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 zero-parameter, no-output-schema tool with no annotations, the description covers purpose, prerequisites, side effects, and when to invoke. The only minor gap is that it never says what a successful or failed refresh looks like to the caller.

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?

The tool takes no parameters, so the schema carries no semantics to supplement and the baseline is 4. The description usefully points at the external inputs that actually matter (environment variable and Keychain service name), which is the closest analogue to parameter documentation here.

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?

The description states a specific verb and resource: re-authenticate to BTWB and replace the stored session cookie. It also distinguishes itself from the rest of the toolset by noting every other tool refreshes automatically, so an agent can tell it is an out-of-band maintenance action rather than a normal data operation.

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 explicitly says you normally don't need to call this directly, then names the two legitimate cases (proactive refresh, verifying credential setup). That is an explicit when-to-use plus an effective default of don't-call, which is exactly what the field asks for.

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