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

Annotations already declare readOnly, idempotent, closed-world, non-destructive behavior, so the safety profile needs no restatement. The description adds genuinely useful behavior beyond that: the comparison window is explicitly Mon–Sun on local dates, and the target value is sourced externally from target_set rather than passed in.

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?

A single sentence that front-loads the action and its operands, with no filler or restatement of the title.

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 no-parameter, fully annotated read tool with no output schema, the description covers what is compared and over what window. It is slightly incomplete on what the comparison actually returns (surplus/deficit, status) and on the behavior when no target has ever been set via target_set.

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?

The tool takes zero parameters, so the baseline is 4. The description goes slightly further by defining the implicit temporal scope (this week, Mon–Sun, local dates) that would otherwise be ambiguous for a parameterless call.

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 (compare), the two resources being compared (hours logged this week vs. the weekly target), and names the sibling that supplies the target (target_set). An agent can distinguish this from summary_week or target_set without opening any schema.

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 clearly establishes the context for use — checking progress against a weekly goal — and names the prerequisite source (target_set). It does not, however, state any exclusions or contrast itself with the other weekly-aggregation siblings such as summary_week, leaving the agent to infer that distinction.

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