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

Beyond the annotations (which only say this is a non-read-only, non-idempotent, non-destructive local operation), the description discloses the hard 24-hour absolute ceiling that TTL renewal cannot exceed and the secrecy requirement on the owner token. It omits what happens on an expired lease or invalid token, which would complete the picture for a non-idempotent mutation.

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?

Five short sentences, front-loaded with the action and the timing condition, with no filler. The final 'No authentication is required' sentence is useful but sits slightly at odds with the required secret owner token, making the ending a touch abrupt.

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?

With an output schema present, return values need no explanation, and the schema fully documents parameters. For a four-parameter mutation with annotations, the description covers purpose, timing, secrecy, and the renewal ceiling — only failure modes (expired lease, wrong owner) are unaddressed.

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%, so key, namespace, owner_token, and ttl_seconds are all documented in the schema itself. The description only echoes the owner-token secrecy and the 24-hour cap, both already present in the schema text, so it adds little parameter meaning beyond structured data.

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 ('Extend') and resource ('lease') with an ownership qualifier ('that this caller still owns'), which meaningfully separates it from acquire_lease, complete_lease, and release_lease. It does not explicitly name any sibling, so differentiation is inferential rather than stated.

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?

'Use it before the current TTL ends when work is still running' gives a clear triggering condition and implicit exclusion (do not call when work is done — use complete_lease/release_lease instead), but those alternatives are never named.

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