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

Annotations already declare readOnly, idempotent, non-destructive and closed-world behavior, so the safety profile is covered. The description's behavioral content is limited to the malformed template fragment 'Returns: {error}', which discloses nothing usable and looks like an unresolved placeholder.

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 definition is short and front-loads the purpose, which is good. But the second sentence, 'Returns: {error}', is broken templating that consumes space without earning it.

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?

An output schema exists, so return values need not be explained, but the description still omits the one thing an agent must know: which combination of inputs is valid. Combined with a 'Returns: {error}' placeholder, the definition is not sufficient to invoke the tool reliably.

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%: a, b and c each have descriptions and minimum:0 constraints, so the baseline is 3. However, the critical semantic — that the caller supplies exactly two sides and receives the third — is absent from both the description and the schema, and with zero required parameters an agent could reasonably call it empty.

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 the missing side of a right triangle via the Pythagorean theorem. This clearly separates it from geometric siblings like calculate_trigonometry or calculate_triangle_heron, though it never names an alternative explicitly.

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 only routing hint is 'See list_bundles for related math calculators', which is a discovery pointer, not usage guidance. It never says when to pick this over calculate_trigonometry or how many sides the caller must supply.

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