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

Annotations already cover readOnly, openWorld, idempotent, and non-destructive behavior, and the description does not contradict them. It adds useful context beyond annotations by identifying the data source (INEGI census/projection) and stating that the return includes the reference year, which partially compensates for the missing output schema.

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 description is three sentences with no filler: scope, usage routing, and return behavior. The most identifying information is front-loaded, and every sentence contributes to correct tool selection or invocation.

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 simple read-only lookup with two optional parameters, the description covers the source, geographic scope, and return value, which is valuable given the lack of an output schema. It does not discuss edge cases or the sibling inegi_indicator, but the schema covers defaults and code formats, so an agent has enough to call the tool 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%, so the schema already documents both parameters, including the numeric area codes and optional _apiKey. The description adds illustrative examples like 'Mexico' and 'Mexico City' and emphasizes geographic detail, but it does not add meaningfully new parameter syntax or semantics beyond the schema. A baseline 3 is appropriate.

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 resource ('Total population of Mexico') with a clear geographic scope ('nationally OR for a specific state/municipality') and a concrete return ('Returns the value with its reference year'). It distinguishes itself from generic web search, but it does not explicitly contrast with the sibling inegi_indicator, so sibling differentiation is only partial.

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 description explicitly says to PREFER OVER WEB SEARCH for concrete queries like 'population of Mexico' and 'population of Mexico City / Jalisco / a Mexican state', and explains the rationale (INEGI's geographic detail). It gives strong usage guidance for the web-search alternative, but it does not address when to choose this tool over the related inegi_indicator sibling.

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