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

With no annotations, the description carries the full burden and does disclose meaningful behavior: the value is read live from a TLS handshake (network dependency, live data), and it states the cost model ($0.02/call in USDC on eip155:8453). It omits failure modes such as timeout, non-443 ports, or unreachable hosts, which would matter for a network probe.

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?

Front-loaded with the value proposition and returned fields, but the final usage sentence ('Use this when an agent needs to days until a certificate expires') restates the opening and contains a grammatical error, adding words without adding information.

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 no output schema, the description correctly enumerates what comes back (days remaining, issuer, validity window, status flag), and pricing is disclosed. For a single-parameter read tool this is nearly complete; only input-format expectations and error behavior are 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?

There is a single required parameter with 100% schema description coverage, so the schema already documents the input. The description adds no format guidance (e.g. bare hostname vs URL vs host:port), which is the one thing an agent would want clarified.

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 (TLS certificate expiry check) and even enumerates the returned fields — days remaining, issuer, validity window, expired/expiring-soon flag. Sibling differentiation is only implicit ('the lightweight check', 'the cheap monitoring primitive'), so an agent must infer that security_ssl_inspector is the heavier alternative rather than being told.

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?

Gives clear context for use: call it on a schedule as a monitoring primitive before a cert lapses, and when the agent just needs days-to-expiry. It does not name the alternative tool (security_ssl_inspector) or state when-not to use this one, so the routing guidance is contextual rather than explicit.

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