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

No annotations are provided, so the description carries the full burden of behavioral disclosure. The description discloses only the return value (UTC timestamp) but hides that the tool apparently performs various validation checks on the 9 parameters (git ref shape, URL normalization, JSON validation, etc.) and that most inputs are 'discarded'. These behaviors are only hinted at in the schema parameter descriptions, not in the tool description, leaving an agent blind to the tool's actual operations and safety profile.

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?

The description is a single short sentence with zero waste, but that brevity is under-specification, not conciseness. A tool with 9 parameters and a validation-like role needs more than 'Current UTC timestamp.' to be intelligible. The description is too thin to earn even a baseline 3.

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?

Given 9 parameters, no annotations, and no output schema, this description is grossly incomplete. It doesn't explain what the parameters do at the tool level, how the tool relates to sibling validation tools, or what the return format is beyond 'timestamp'. An agent has no way to know if this is a pure clock or a hidden validation orchestrator.

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% — all 9 parameters have descriptions in the schema, which is the baseline 3. The tool-level description adds nothing about parameters, but the schema's per-parameter descriptions are reasonably informative (e.g., 'discarded after the shape check', 'no disk access'). The description doesn't need to duplicate what the schema covers.

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 'Current UTC timestamp' states a clear output (the current UTC time) with an implied verb, so it's not a tautology. However, the tool accepts 9 parameters for seemingly unrelated checks (git refs, URLs, cities, JSON, paths) that the description never mentions, making the tool's overall purpose ambiguous. It also doesn't differentiate from sibling tools like 'timezone' or 'tz-america-lima', which likely return related time data.

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 provides no guidance on when to use this tool versus alternatives like 'timezone', 'tz-america-lima', or the various shape-checking siblings (domain-shape, github-repo-shape, etc.). No when/when-not conditions, no exclusions, no context about why the 9 parameters exist. An agent cannot decide when to select this tool over a sibling.

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