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

Annotations already declare readOnlyHint, idempotentHint and destructiveHint=false, so the safety profile is covered. The description adds genuine context by naming the auth mechanism (account cookie sent in the MCP request) and the account model, but it does not describe what the counters contain or what the response looks like.

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?

Two short sentences, front-loaded with the core purpose, no filler or repetition. It is efficient, though the terseness borders on cryptic given the undefined 'contadores'.

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?

Complexity is low (read-only, one optional param), which keeps the bar modest, but there is no output schema and the description only generically mentions 'identity and counters'. An agent cannot tell what fields or counters to expect, leaving a real gap.

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 100%: the sole optional parameter 'locais' is fully documented in the schema (up to 90 comma-separated document IDs, max 1529 chars, checks ownership). The description adds nothing about this parameter, so the baseline of 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 identifies the resource as session identity plus private counters tied to the account cookie, which is more than a restatement of the title. However, 'contadores privados' is left undefined (counters of what?), and there is no differentiation from near siblings like conta_acompanhamento or minhas_empresas. An agent gets a rough idea but not a precise scope.

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?

No when-to-use, when-not-to-use, or alternative tool is stated. The remark that 'the global account is already the person, there is no per-product activation' clarifies the account model but does not tell an agent when to call this tool versus another account-related sibling.

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