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

readOnlyHint=true already establishes the safety profile, so the description's job is supplemental — and it adds real value: the output is mechanical numbers, cost basis is split-adjusted, no advisory interpretation is intended, and the response carries an app link. It does not cover auth/scope requirements or empty-portfolio 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 sentences, front-loaded with what is returned, then the guardrail, then the hand-off note. The 'NOT analysis, a rating, or investment advice' clause is slightly redundant but serves a real agent-behavior purpose; otherwise no waste.

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?

With no output schema, the description carries the return-value burden and does so adequately by naming holdings, cost basis, totals, unrealized P/L, and the app link. It omits edge cases such as an empty or unavailable portfolio, which would fully round it out.

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?

The tool takes zero parameters, so the baseline is 4 by rule; there is no parameter surface for the description to explain or fail to explain.

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 ('Get the signed-in user's own Returnolio portfolio') and enumerates the aggregation content (holdings with weighted-average, split-adjusted cost basis, totals, unrealized P/L). This clearly separates it from siblings like compare_stocks, screen_stocks, or my_watchlist.

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?

Explicitly frames the tool as a 'numbers-only readout, NOT analysis, a rating, or investment advice,' which rules out use cases an agent might otherwise route here (e.g., score/rating requests belong to get_stock_score). It also notes holdings edits happen in the app, but it does not name a sibling tool as the alternative for any specific need.

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