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

Goes meaningfully beyond the annotations by disclosing the authorization requirement ('write access'), a hard behavioral ceiling (cannot exceed the existing absolute deadline), and failure semantics for expired keys (no revival). This adds real context beyond readOnlyHint=false and destructiveHint=false. It does not explain the interaction with if_match or what happens on a stale match.

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?

Two short, front-loaded sentences with no filler; the core action comes first and the constraints follow in order of importance.

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?

A mutation tool with no output schema and zero parameter descriptions needs more from the description than two lines. Return values (whether the TTL was renewed, remaining deadline, mismatch behavior) and the semantics of if_match, ttl_mode, and ttl_seconds are all absent, so an agent cannot call this confidently beyond the simplest case.

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?

With schema description coverage at 0%, four parameters are undocumented in structured fields and the description must compensate. It only hints at ttl_mode/ttl_seconds via 'absolute deadline' and says nothing about 'key' syntax or the purpose of 'if_match' (presumably optimistic concurrency). Most of the parameter surface is left unexplained.

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+resource ('Renew TTL') plus the operative constraint ('within the existing absolute deadline'). This distinguishes it from siblings like put_key or create_key, which write values rather than lifecycle state, though no sibling is named explicitly.

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?

The description implies when it applies by bounding the operation ('within the existing absolute deadline', 'Never revive expired keys'), which effectively tells the agent when the call is a no-op. It never states when to choose touch_key over patch_key or put_key when the goal is to change TTL, so alternatives remain inferred.

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