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 adds a genuinely non-obvious side-effect fact ('Reading does not fire the portfolio's webhooks') and describes the shape of what comes back, which matters because no output schema exists. It stops short of pagination or rate-limit 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?

Front-loaded with purpose, then the return contents, then the prerequisite and side-effect note. It is one long dense sentence with no wasted clauses, though the packing of counts, per-signal fields and cause taxonomy into a single sentence is slightly heavy for scanning.

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 burden of explaining returns and does so thoroughly (counts of places checked/changes found, per-place signals with direction, from/to, delta, percent change, cause). The prerequisite id source and the webhook side-effect are also covered; only error behavior and large-portfolio handling are absent.

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%, so the schema already documents all five parameters including enum meanings for cause and baseline and the defaults for threshold_pct and min_transactions. The description restates the cause semantics (source data moved vs. a named methodology release) and the baseline/threshold concept but adds no syntax or format detail beyond the schema, so the baseline 3 applies.

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 (reports) and resource (material signal changes across a portfolio between two periods), and enumerates the returned content (baseline/threshold used, counts, per-place signal movements). Combined with the portfolio-scoped framing and the reference to watch_portfolio, an agent can distinguish this from area-level siblings like get_area_signals without opening the schema.

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 prerequisite is stated ('Needs a portfolio id from watch_portfolio'), which is real usage context, but there is no explicit when-to-use versus when-not, and no alternative is named for the case where an agent wants per-area rather than per-portfolio changes. Usage is implied rather than routed.

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