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

With no annotations, the description carries the full burden and does well: it discloses encryption at rest, that password and TOTP secret are never returned by any tool, and the free-tier behavior ('stores nothing and logs would_use_vault'). It does not say what happens when a login with the same name already exists (overwrite vs. error) or what save_login itself returns.

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?

Four dense sentences, front-loaded with the owner-only precondition, and every sentence carries information (auth, encryption, environment, tier behavior). Slightly packed but 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 mutation tool with no annotations and no output schema, the description covers permissions, environment, security guarantees, and free-tier divergence. The remaining gap is idempotency/duplicate-name behavior, which an agent needs before re-saving the same login.

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 coverage is 67%, so the schema already documents most fields. The description enumerates the scope contents (allowed hosts, allowed methods, daily cap, session TTL), but this largely restates the nested schema descriptions rather than adding format, bounds, or interaction semantics.

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 ('Store one login') plus the mechanism (sealed with AES-256-GCM). It is clearly distinguishable from siblings like list_logins, delete_login, and open_session, which operate on already-stored or session-level resources.

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 constrains the caller ('Owner only... never a bot key') and the execution environment ('Run it from your own machine, not inside the bot'), which is real when/when-not guidance. It stops short of naming alternative tools for related tasks, so it does not reach 5.

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