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

Annotations already declare readOnlyHint=true, destructiveHint=false, and openWorldHint=false, so the safety profile is covered. The description still adds real context by disclosing what is computed (monthly payment, total paid, interest) and the conditional rate logic per mortgage type, though it says nothing about input rejection or rounding behavior.

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, front-loaded with the core output and then the per-mode parameter routing. No filler and every clause carries information an agent needs.

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 an 8-parameter calculation tool with no output schema and annotations covering safety, the description adequately covers the modes and outputs. The only mild gap is that it does not explain plazo_anos or the annual amortization table flag, but these are self-evident from their schema descriptions.

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?

At 75% schema coverage the schema documents most parameters, so the baseline is 3. The description exceeds it by explaining the cross-parameter dependency between tipo and which rate fields to supply for each mode, which the schema does not spell out; plazo_anos remains undocumented in the description.

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 states a specific verb+resource: it computes the monthly payment (cuota mensual), total paid, and interest for a fixed, variable, or mixed mortgage, and it names the three rate modes. It is clear what the tool produces, but it never distinguishes itself from siblings such as mortgage_calcular_capacidad or mortgage_simular_primera_vivienda.

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?

It gives strong per-mode invocation guidance (Fija: tin; Variable: euribor + diferencial; Mixta: tin during anos_fijos then euríbor + diferencial), which is essentially 'which parameters to use when'. However it gives no guidance on when to choose this tool over alternative mortgage tools, so usage context is only implied.

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