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

Annotations already cover the safety profile (readOnly, idempotent, non-destructive), so the bar is lower; the description still adds the return unit ('period in seconds') and the gravity default of 9.81, plus the governing formula. No caveats about validity range (small-angle approximation) or invalid inputs, keeping it from a 5.

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?

Three short sentences with the formula and primary input front-loaded; nothing is padded. Slight redundancy in re-listing inputs that the schema already documents costs it a point.

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 two-parameter, fixed-formula calculator with an output schema present, the definition covers model, inputs, defaults, output unit, and a related-bundle pointer. An agent has everything needed to call it correctly.

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 coverage is 100% and both parameters are already documented with units and defaults in the schema. The description restates 'length m, gravity m/s² (default 9.81)' without adding constraint meaning such as the minimum 0.01 m or the small-angle domain. Baseline 3 applies when the schema carries the load.

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 ('Compute simple pendulum period') plus the exact formula T=2π√(L/g), which pins down the physics model and separates it from near-neighbors like calculate_spring_constant or calculate_projectile_motion. It does not explicitly contrast with any sibling tool, so it lands just short of a 5.

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 for physics homework or clock design' implies a domain but gives no when-not conditions and names no alternative tool for adjacent physics calculations. The list_bundles pointer is a cross-reference, not usage guidance, so usage is only implied.

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