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

Annotations already cover readOnly/openWorld/destructive, but the description adds real behavioral context beyond them: no API key required for base data, and AI enrichment fields (ai_summary, fiscal_signals) are gated behind a paid plan. That tiering is exactly what an agent needs to interpret partial results, though reversibility/rate-limit detail is absent (mostly irrelevant for a read).

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?

Front-loaded with the returned payload, then short sentences for key requirement, paid-plan gating, and parameter format. Dense but every clause carries information; no filler.

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 single-record lookup with no output schema and full annotation coverage, the description tells the agent what fields come back, that no key is needed, that some fields are paywalled, and how to format the code. Little is missing that the structured fields don't already supply.

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 description coverage is 0%, so the description must compensate for the single 'code' parameter. It does: gives an example value ('B831'), explains the qualified-code format, and states the reason for it (disambiguating epígrafes with several sections). Meaningfully more than the bare pattern in the 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?

Names a specific resource (IAE epígrafe record) and enumerates its contents: título, descripción, elegibilidad de módulos, correspondencia IAE↔CNAE 2025, url. An agent knows it returns a single record's detail. It never names a sibling (e.g. detalle_cnae) as a contrast, so it stops short of full cross-tool differentiation.

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 implied by the resource: fetch one IAE epígrafe's detail. The disambiguation hint ('Acepta un código cualificado... para desambiguar epígrafes con varias secciones') gives situational guidance, but there is no explicit when-to-use-this-vs-detalle_cnae/buscar_codigo routing or stated prerequisites.

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