stats

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

No annotations are supplied, so the description carries the behavioral burden. It implies a read-only aggregation but never states that no data is modified, nor how the window is scoped (lifetime vs. recent), how 'current streak' is computed across time zones or gaps, or how many 'top tags' are returned. For a zero-parameter tool the gap is modest but real.

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 front-loaded sentence with a colon-delimited list of returned metrics and no filler. Every clause earns its place and the reader knows what comes back immediately.

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 bears responsibility for describing the return payload, and it does list the four metrics. Remaining gaps are the ambiguity of 'top tags' (how many, ranked by what) and the window over which totals and streaks are computed, which an agent might need before citing results.

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 there is no parameter semantics to explain and the baseline of 4 applies. Nothing in the description conflicts with the empty schema.

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 names the resource (diary) and enumerates the exact metrics returned: total entries, active days, current streak, and top tags. That is concrete enough for an agent to distinguish it from mutation siblings like log_work or edit_entry. It stops short of explicitly contrasting with daily_summary, which also returns summary-style 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?

Usage is only implied: an agent infers this is the tool for aggregate diary metrics rather than entry-level retrieval. There is no statement about when to prefer it over daily_summary, nor any note that it takes no parameters and therefore returns a global view. Adequate but leaves the sibling choice to inference.

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